Border Gateway Protocol - Knowledge (XXG)

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community attribute content. The definition of this Extended Community Attribute is documented in RFC 4360. The IANA administers the registry for BGP Extended Communities Types. The Extended Communities Attribute itself is a transitive optional BGP attribute. A bit in the type field within the attribute decides whether the encoded extended community is of a transitive or non-transitive nature. The IANA registry therefore provides different number ranges for the attribute types. Due to the extended attribute range, its usage can be manifold. RFC 4360 exemplarily defines the "Two-Octet AS Specific Extended Community", the "IPv4 Address Specific Extended Community", the "Opaque Extended Community", the "Route Target Community", and the "Route Origin Community". A number of BGP QoS drafts also use this Extended Community Attribute structure for inter-domain QoS signalling.

3124:, is an extension to BGP that allows different types of addresses (known as address families) to be distributed in parallel. Whereas standard BGP supports only IPv4 unicast addresses, Multiprotocol BGP supports IPv4 and IPv6 addresses and it supports unicast and multicast variants of each. Multiprotocol BGP allows information about the topology of IP multicast-capable routers to be exchanged separately from the topology of normal IPv4 unicast routers. Thus, it allows a multicast routing topology different from the unicast routing topology. Although MBGP enables the exchange of inter-domain multicast routing information, other protocols such as the Protocol Independent Multicast family are needed to build trees and forward multicast traffic. 2567:

damping may not be as important as it used to be, since changes to the routing table can be handled much faster by routers. This has led the RIPE Routing Working Group to write, "With the current implementations of BGP flap damping, the application of flap damping in ISP networks is NOT recommended. ... If flap damping is implemented, the ISP operating that network will cause side-effects to their customers and the Internet users of their customers' content and services ... . These side-effects would quite likely be worse than the impact caused by simply not running flap damping at all." Improving stability without the problems of flap damping is the subject of current research.

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OpenSent state if successful. If unsuccessful, it starts the ConnectRetry timer and transitions to the Active state upon expiration. In the Active state, the router resets the ConnectRetry timer to zero and returns to the Connect state. In the OpenSent state, the router sends an Open message and waits for one in return in order to transition to the OpenConfirm state. Keepalive messages are exchanged and, upon successful receipt, the router is placed into the Established state. In the Established state, the router can send and receive: Keepalive; Update; and Notification messages to and from its peer.

2417:(RRs) reduce the number of connections required in an AS. A single router (or two for redundancy) can be made an RR: other routers in the AS need only be configured as peers to them. An RR offers an alternative to the logical full-mesh requirement of iBGP. The purpose of the RR is concentration. Multiple BGP routers can peer with a central point, the RR – acting as an RR server – rather than peer with every other router in a full mesh. All the other iBGP routers become RR clients. 2555:. At the first instance when a route becomes unavailable and quickly reappears, damping does not take effect, so as to maintain the normal fail-over times of BGP. At the second occurrence, BGP shuns that prefix for a certain length of time; subsequent occurrences are ignored exponentially longer. After the abnormalities have ceased and a suitable length of time has passed for the offending route, prefixes can be reinstated with a clean slate. Damping can also mitigate 3143:. This typically requires identical MED, weight, origin, and AS-path although some implementations provide the ability to relax the AS-path checking to only expect an equal path length rather than the actual AS numbers in the path being expected to match too. This can then be extended further with features like Cisco's dmzlink-bw which enables a ratio of traffic sharing based on bandwidth values configured on individual links. 2424:'s DR/BDR feature, provides large networks with added iBGP scalability. In a fully meshed iBGP network of 10 routers, 90 individual CLI statements (spread throughout all routers in the topology) are needed just to define the remote-AS of each peer: this quickly becomes a headache to manage. An RR topology can cut these 90 statements down to 18, offering a viable solution for the larger networks administered by ISPs. 2576: 3108:. Due to the extent to which BGP is embedded in the core systems of the Internet, and the number of different networks operated by many different organizations which collectively make up the Internet, correcting this vulnerability (such as by introducing the use of cryptographic keys to verify the identity of BGP routers) is a technically and economically challenging problem. 2584: 746:(FSM) that consists of six states: Idle; Connect; Active; OpenSent; OpenConfirm; and Established. For each peer-to-peer session, a BGP implementation maintains a state variable that tracks which of these six states the session is in. The BGP defines the messages that each peer should exchange in order to change the session from one state to another. 930: 52: 2449: 2500:

confederation preserves next hop, metric, and local preference information. To the outside world, the confederation appears to be a single AS. With this solution, iBGP transit AS problems can be resolved as iBGP requires a full mesh between all BGP routers: large number of TCP sessions and unnecessary duplication of routing traffic.

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natively has no concept to allow one AS to tell another AS to restrict advertisement of a prefix to only North American peering customers. Instead, an ISP generally publishes a list of well-known or proprietary communities with a description for each one, which essentially becomes an agreement of how prefixes are to be treated.

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this approach when a route flaps inside an autonomous system, it is not propagated to the external ASs – flapping a route to an eBGP will cause a chain of flapping for the particular route throughout the backbone. This method also successfully avoids the overhead of route flap damping for iBGP sessions.

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depends on the amount of BGP information exchanged with other BGP speakers and the way in which the particular router stores BGP information. The router may have to keep more than one copy of a route, so it can manage different policies for route advertising and acceptance to a specific neighboring AS. The term

2551:) is built into many BGP implementations in an attempt to mitigate the effects of route flapping. Without damping, the excessive activity can cause a heavy processing load on routers, which may in turn delay updates on other routes, and so affect overall routing stability. With damping, a route's flapping is 2592:

table, these routers will cease to be effective gateways between the parts of the Internet they connect. In addition, and perhaps even more importantly, larger routing tables take longer to stabilize after a major connectivity change, leaving network service unreliable, or even unavailable, in the interim.

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The routing tables managed by a BGP implementation are adjusted continually to reflect actual changes in the network, such as links or routers going down and coming back up. In the network as a whole, it is normal for these changes to happen almost continuously, but for any particular router or link,

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With the introduction of 32-bit AS numbers, some issues were immediately obvious with the community attribute that only defines a 16-bit ASN field, which prevents the matching between this field and the real ASN value. Since RFC 7153, extended communities are compatible with 32-bit ASNs. RFC 8092 and

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attribute (see below) is not directly used by the BGP selection process. The BGP neighbor process can have a rule to set local preference or another factor based on a manually programmed rule to set the attribute if the community value matches some pattern-matching criterion. If the route was learned

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Next, for each neighbor, the BGP process applies various standard and implementation-dependent criteria to decide which routes conceptually should go into the Adj-RIB-In. The neighbor could send several possible routes to a destination, but the first level of preference is at the neighbor level. Only

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A BGP router used only for a network with a single point of entry to the Internet may have a much smaller routing table size (and hence RAM and CPU requirement) than a multihomed network. Even simple multihoming can have modest routing table size. The actual amount of memory required in a BGP router

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routes, and making the routing table reach 515,000 entries. The new routes appear to have been reaggregated within 5 minutes, but instability across the Internet apparently continued for a number of hours. Even if Verizon had not caused the routing table to exceed 512k entries in the short spike, it

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MEDs, defined in the main BGP standard, were originally intended to show to another neighbor AS the advertising AS's preference as to which of several links are preferred for inbound traffic. Another application of MEDs is to advertise the value, typically based on delay, of multiple ASs that have a

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The customer simply adjusts their configuration to include the correct community or communities for each route, and the ISP is responsible for controlling who the prefix is advertised to. The end user has no technical ability to enforce correct actions being taken by the ISP, though problems in this

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One of the largest problems faced by BGP, and indeed the Internet infrastructure as a whole, is the growth of the Internet routing table. If the global routing table grows to the point where some older, less capable routers cannot cope with the memory requirements or the CPU load of maintaining the

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Subsequent research has shown that flap damping can actually lengthen convergence times in some cases, and can cause interruptions in connectivity even when links are not flapping. Moreover, as backbone links and router processors have become faster, some network architects have suggested that flap

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It is also suggested in RFC 2439 that route flap damping is a feature more desirable if implemented to Exterior Border Gateway Protocol Sessions (eBGP sessions or simply called exterior peers) and not on Interior Border Gateway Protocol Sessions (iBGP sessions or simply called internal peers). With

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Whenever a conceptual Adj-RIB-In changes, the main BGP process decides if any of the neighbor's new routes are preferred to routes already in the Loc-RIB. If so, it replaces them. If a given route is withdrawn by a neighbor, and there is no other route to that destination, the route is removed from

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As the prospect of system meltdown loomed, the men began scribbling ideas for a solution onto the back of a ketchup-stained napkin. Then a second. Then a third. The "three-napkins protocol", as its inventors jokingly dubbed it, would soon revolutionize the Internet. And though there were lingering

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networks. It is not a trivial task to balance the inbound traffic to a multi-homed network across its multiple inbound paths, due to limitation of the BGP route selection process. For a multi-homed network, if it announces the same network blocks across all of its BGP peers, the result may be that

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as routers attempted to compensate for the issue by using slow software routing (as opposed to fast hardware routing via TCAM). The main method for dealing with this issue involves operators changing the TCAM allocation to allow more IPv4 entries, by reallocating some of the TCAM reserved for IPv6

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can cause excessive activity in all the other routers that know about the cycling entity, as the same route is continually injected and withdrawn from the routing tables. The BGP design is such that delivery of traffic may not function while routes are being updated. On the Internet, a BGP routing

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The BGP Extended Community Attribute was added in 2006, in order to extend the range of such attributes and to provide a community attribute structuring by means of a type field. The extended format consists of one or two octets for the type field followed by seven or six octets for the respective

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The first state is the Idle state. In the Idle state, BGP initializes all resources, refuses all inbound BGP connection attempts and initiates a TCP connection to the peer. The second state is Connect. In the Connect state, the router waits for the TCP connection to complete and transitions to the

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If one router implementation takes more memory per route than another implementation, this may be a legitimate design choice, trading processing speed against memory. A full IPv4 BGP table as of August 2015 is in excess of 590,000 prefixes. Large ISPs may add another 50% for internal and customer

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BGP communities are attribute tags that can be applied to incoming or outgoing prefixes to achieve some common goal. While it is common to say that BGP allows an administrator to set policies on how prefixes are handled by ISPs, this is generally not possible, strictly speaking. For instance, BGP

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BGP submits the routes that it considers best to the main routing table process. Depending on the implementation of that process, the BGP route is not necessarily selected. For example, a directly connected prefix, learned from the router's own hardware, is usually most preferred. As long as that

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To work around this problem, BGP administrators of that multihomed network may divide a large contiguous IP address block into smaller blocks and tweak the route announcement to make different blocks look optimal on different paths, so that external networks will choose a different path to reach

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By default Internal IGP is not added. Can be set to add IGP metric. Before the most recent edition of the BGP standard, if an update had no MED value, several implementations created a MED with the highest possible value. The current standard specifies that missing MEDs are treated as the lowest

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The physical storage and structure of these conceptual tables are decided by the implementer of the BGP code. Their structure is not visible to other BGP routers, although they usually can be interrogated with management commands on the local router. It is quite common, for example, to store the

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It is a common tactic for end customers to use BGP communities (usually ASN:70,80,90,100) to control the local preference the ISP assigns to advertised routes instead of using MED (the effect is similar). The community attribute is transitive, but communities applied by the customer very rarely

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The BGP standard specifies a number of decision factors, more than the ones that are used by any other common routing process, for selecting NLRI to go into the Loc-RIB. The first decision point for evaluating NLRI is that its next-hop attribute must be reachable (or resolvable). Another way of

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and various recovery modes. If the multiprotocol extensions to BGP are negotiated at the time of creation, the BGP speaker can prefix the Network Layer Reachability Information (NLRI) it advertises with an address family prefix. These families include the IPv4 (default), IPv6, IPv4/IPv6 Virtual

2406:(where everyone speaks to everyone directly). This full-mesh configuration requires that each router maintain a session with every other router. In large networks, this number of sessions may degrade the performance of routers, due to either a lack of memory, or high CPU process requirements. 2499:

The confederated AS is composed of multiple ASs. Each confederated AS alone has iBGP fully meshed and has connections to other ASs inside the confederation. Even though these ASs have eBGP peers to ASs within the confederation, the ASs exchange routing as if they used iBGP. In this way, the

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Continue, even if bestpath is already selected. Prefer the route with the lowest interior cost to the next hop, according to the main routing table. If two neighbors advertised the same route, but one neighbor is reachable via a low-bitrate link and the other by a high-bitrate link, and the

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If there is an error it is because one of the fields in the OPEN or UPDATE message does not match between the peers, e.g., BGP version mismatch, the peering router expects a different My AS, etc. The router then sends a Notification message to the peer indicating why the error occurred.

2647:, for storing BGP advertised routes. On impacted routers, the TCAM was by default allocated as 512k IPv4 routes and 256k IPv6 routes. While the reported number of IPv6 advertised routes was only about 20k, the number of advertised IPv4 routes reached the default limit, causing a 725:

mechanism. This mechanism consists of a set of rules. Each rule describes, for routes matching some given criteria, what action should be taken. The action could be to drop the route, or it could be to modify some attributes of the route before inserting it in the routing table.

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By design, routers running BGP accept advertised routes from other BGP routers by default. This allows for automatic and decentralized routing of traffic across the Internet, but it also leaves the Internet potentially vulnerable to accidental or malicious disruption, known as

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Confederations are sets of autonomous systems. In common practice, only one of the confederation AS numbers is seen by the Internet as a whole. Confederations are used in very large networks where a large AS can be configured to encompass smaller more manageable internal ASs.

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If there is an error it is because one of the fields in the Open message does not match between the peers, e.g., BGP version mismatch, the peering router expects a different My AS, etc. The router then sends a Notification message to the peer indicating why the error

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Products marketed as switches may have a size limitation on BGP tables that is far smaller than a full Internet table plus internal routes. These devices may be perfectly reasonable and useful when used for BGP routing of some smaller part of the network, such as a

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In the simplest arrangement, all routers within a single AS and participating in BGP routing must be configured in a full mesh: each router must be configured as a peer to every other router. This causes scaling problems, since the number of required connections

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Additionally, route reflectors and BGP confederations were not designed to ease BGP router configuration. Nevertheless, these are common tools for experienced BGP network architects. These tools may be combined, for example, as a hierarchy of route reflectors.

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directly connected route's interface is active, the BGP route to the destination will not be put into the routing table. Once the interface goes down, and there are no more preferred routes, the Loc-RIB route would be installed in the main routing table.

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The RFC 1771 BGP-4 specification coded AS numbers on 16 bits, for 64,510 possible public AS numbers. In 2011, only 15,000 AS numbers were still available, and projections were envisioning a complete depletion of available AS numbers in September 2013.

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We show that the current damping design leads to the intended behavior only under persistent route flapping. When the number of flaps is small, the global routing dynamics deviates significantly from the expected behavior with a longer convergence

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RFC 6793 extends AS coding from 16 to 32 bits, which now allows up to 4 billion available AS. An additional private AS range is also defined in RFC 6996. To allow the traversal of router groups not able to manage those new ASNs, the new attribute

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Confederations can be used in conjunction with route reflectors. Both confederations and route reflectors can be subject to persistent oscillation unless specific design rules, affecting both BGP and the interior routing protocol, are followed.

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possible value. Since the current rule may cause different behavior than the vendor interpretations, BGP implementations that used the nonstandard default value have a configuration feature that allows the old or standard rule to be selected.

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one or several of its inbound links become congested while the other links remain under-utilized, because external networks all picked that set of congested paths as optimal. Like most other routing protocols, BGP does not detect congestion.

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is then attached to every route advertised by the RR to its client or nonclient peers. A cluster ID is a cumulative, non-transitive BGP attribute, and every RR must prepend the local cluster ID to the cluster list to avoid routing loops.

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RRs and confederations both reduce the number of iBGP peers to each router and thus reduce processing overhead. RRs are a pure performance-enhancing technique, while confederations also can be used to implement more fine-grained policy.

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While a full IPv4 BGP table as of August 2014 (512k day) was in excess of 512,000 prefixes, many older routers had a limit of 512k (512,000–524,288) routing table entries. On August 12, 2014, outages resulting from full tables hit

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statements in this case. In a BGP multipath environment the additional RR also can benefit the network by adding local routing throughput if the RRs are acting as traditional routers instead of just a dedicated RR server role.

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changes are expected to be relatively infrequent. If a router is misconfigured or mismanaged then it may get into a rapid cycle between down and up states. This pattern of repeated withdrawal and re-announcement known as

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Type: UPDATE Message (2) Withdrawn Routes Length: 0 Total Path Attribute Length: 25 Path attributes ORIGIN: IGP AS_PATH: 64500 NEXT_HOP: 192.0.2.254 MULTI_EXIT_DISC: 0 Network Layer Reachability Information (NLRI)

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the Loc-RIB and no longer sent by BGP to the main routing table manager. If the router does not have a route to that destination from any non-BGP source, the withdrawn route will be removed from the main routing table.

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L3 VPN, to exchange VPN labels learned for the routes from the customer sites over the MPLS network, in order to distinguish between different customer sites when the traffic from the other customer sites comes to the

3163:(OSPF) networks when OSPF by itself does not scale to the size required. Another reason to use BGP is multihoming a network for better redundancy, either to multiple access points to a single ISP or to multiple ISPs. 2431:, therefore at least a second RR may be configured in order to provide redundancy. As it is an additional peer for the other 10 routers, it approximately doubles the number of CLI statements, requiring an additional 1403:

The local preference, weight, and other criteria can be manipulated by local configuration and software capabilities. Such manipulation, although commonly used, is outside the scope of the standard. For example, the

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179. A BGP speaker sends 19-byte keep-alive messages every 30 seconds (protocol default value, tunable) to maintain the connection. Among routing protocols, BGP is unique in using TCP as its transport protocol.

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If an error occurs at any state of the FSM process, the BGP session is terminated immediately and returned to the Idle state. Some of the reasons why a router does not progress from the Idle state are:

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Optional Parameters Length: 16 Optional Parameters: Capability: Multiprotocol extensions capability (1) Capability: Route refresh capability (2) Capability: Route refresh capability (Cisco) (128)

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together in the same data structure, with additional information attached to the RIB entries. The additional information tells the BGP process such things as whether individual entries belong in the

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BGP carries the information with which rules inside BGP-speaking routers can make policy decisions. Some of the information carried that is explicitly intended to be used in policy decisions are:

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Type: ROUTE-REFRESH Message (5) Address family identifier (AFI): IPv4 (1) Subtype: Normal route refresh request with/without ORF (0) Subsequent address family identifier (SAFI): Unicast (1)

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Private Networks and multicast BGP. Increasingly, BGP is used as a generalized signaling protocol to carry information about routes that may not be part of the global Internet, such as VPNs.

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is often used to improve aggregation of the BGP global routing table, thereby reducing the necessary table size in routers of an AS. Consider AS1 has been allocated the big address space of

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The actual allocations which pushed the number of routes above 512k was the announcement of about 15,000 new routes in short order, starting at 07:48 UTC. Almost all of these routes were to

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to limited the number of specific routes to all of internet. For multi-home AS, that have 2 or more neighbour, that like to load balance, where they will specific a more detailed route.

3175:(SOHO) use, may not include BGP capability. Other commercial routers may need a specific software executable image that supports BGP, or a license that enables it. Devices marketed as 1100:

saying the next-hop must be reachable is that there must be an active route, already in the main routing table of the router, to the prefix in which the next-hop address is reachable.

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from an external peer the per-neighbor BGP process computes a local preference value from local policy rules and then compares the local preference of all routes from the neighbor.

2599:, threatening an eventual widespread breakdown of connectivity. In an attempt to prevent this, ISPs cooperated in keeping the global routing table as small as possible, by using 1104:

one route to each destination will be installed in the conceptual Adj-RIB-In. This process will also delete, from the Adj-RIB-In, any routes that are withdrawn by the neighbor.

4209: 4271: 948: 2694:, this would be counted as one route in the table, but due to customer requirements or traffic engineering purposes, AS1 wants to announce smaller, more specific routes of 1191:

If there are several iBGP routes from the neighbor, the one with the highest local preference is selected unless there are several routes with the same local preference.

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in 2006. RFC 4271 corrected errors, clarified ambiguities and updated the specification with common industry practices. The major enhancement of BGP4 was the support for

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AS jumps is the number of AS numbers that must be traversed to reach the advertised destination. AS1–AS2–AS3 is a shorter path with fewer jumps than AS4–AS5–AS6–AS7.

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The main difference between iBGP and eBGP peering is in the way routes that were received from one peer are typically propagated by default to other peers:

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issues, the engineers saw their creation as a "hack" or "kludge", slang for a short-term fix to be replaced as soon as a better alternative arrived.

2945:, the number of routes AS1 announces drops to three. Depending on the routing policy of AS2, it will store a copy of the three routes, or aggregate 3487: 4352: 3095:

to allow ingress traffic engineering across multiple links. This technique does not increase the number of routes seen on the global BGP table.

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KeepAlive messages are sent periodically, to verify that remote peer is still alive. keepalives should be sent at intervals of one third the

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Type: NOTIFICATION Message (3) Major error Code: OPEN Message Error (2) Minor error Code (Open Message): Bad Peer AS (2) Bad Peer AS: 65200

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The Border Gateway Protocol was sketched out in 1989 by engineers on the back of "three ketchup-stained napkins", and is still known as the

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During the peering handshake, when OPEN messages are exchanged, BGP speakers can negotiate optional capabilities of the session, including

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If a timer expires before a Keepalive message is received, or if an error condition occurs, the router transitions back to the Idle state.

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These route-propagation rules effectively require that all iBGP peers inside an AS are interconnected in a full mesh with iBGP sessions.

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If there is any error in the Update message then a Notification message is sent to the peer, and BGP transitions back to the Idle state.

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If a Keepalive message is received and no timer has expired before reception of the Keepalive, BGP transitions to the Established state.

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calculates lowest cost based on highest bitrate, the route through the high-bitrate link would be preferred and other routes dropped.

416: 359: 284: 3032:, it will be dropped or a destination unreachable ICMP message will be sent back at the routers of AS2 (not AS1 as before), because 2883: 966: 426: 396: 3972: 480: 411: 204: 4456: 3763: 1016:: local routing information base BGP maintains its own master routing table separate from the main routing table of the router. 4530: 4900: 4088: 3450: 3084:

different blocks of that multi-homed network. Such cases will increase the number of routes as seen on the global BGP table.

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RFC 8195 introduce a Large Community attribute of 12 bytes, divided in three field of 4 bytes each (AS:function:parameter).

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from multiple neighbors and advertise NLRI to the same, or a different set, of neighbors. The BGP process maintains several

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Repeated failures may result in a router cycling between the Idle and Active states. Some of the reasons for this include:

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By default only route with the same autonomous system (AS) is compared. Can be set to ignore same autonomous system (AS).

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BGP FSM tries to restart another TCP session with the peer and, if successful, then it sends an Open message to the peer.

3218: 2659: 2607:. While this slowed the growth of the routing table to a linear process for several years, with the expanded demand for 2026: 1087: 910:

In this state, the peers send Update messages to exchange information about each route being advertised to the BGP peer.

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Multiprotocol Extensions for BGP (MBGP), sometimes referred to as Multiprotocol BGP or Multicast BGP and defined in

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for specific neighbors, whether the peer-neighbor route selection process made received policies eligible for the

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If there is no error, a Keepalive message is sent, various timers are set and the state is changed to OpenConfirm.

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routes, which requires a reboot on most routers. The 512k problem was predicted by a number of IT professionals.

1325: 515: 103: 3172: 3160: 2556: 1784: 1649: 1000: 299: 239: 2823:) and it is up to the routing policy of AS2 to decide whether or not to take a copy of the four routes or, as 3557: 3211:

routes. Again depending on implementation, separate tables may be kept for each view of a different peer AS.

3365: 3092: 2428: 466: 456: 249: 148: 4644:, Standards Maturity Variance Regarding the TCP MD5 Signature Option (RFC 2385) and the BGP-4 Specification 3192: 1616:

Allow for faster recovery of connectivity on different types of failures, with multicast in BGP/MPLS VPNs.

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An autonomous system with internal BGP (iBGP) must have all of its iBGP peers connect to each other in a

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If the router was unable to establish a successful TCP session, then it ends up in the Active state.

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tunnel, allowing two remote sites to exchange routing information in a secure and isolated manner.

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Another factor contributing to the growth of the routing table is the need for load balancing of

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701 and 705, created as a result of deaggregation of larger blocks, introducing thousands of new

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BGP does not spend much time in this state if the TCP session has been successfully established.

534:, and it makes routing decisions based on paths, network policies, or rule-sets configured by a 4298: 4110: 3330: 3290: 3238: 3140: 2620: 2604: 2552: 2069:

Only changes are sent, after initial exchange, only difference (add/change/removed) are sent.

1977: 989: 735: 621: 605: 569:. It was first described in 1989 in RFC 1105, and has been in use on the Internet since 1994. 379: 155: 115: 74: 4796:, Obsolete – Definitions of Managed Objects for the Fourth Version of the Border Gateway 4413: 4236: 3514:"Net of Insecurity; Quick fix for an early Internet problem lives on a quarter-century later" 1065:

entries are eligible to be submitted to the local router's routing table management process.

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Systems for testing BGP conformance, load or stress performance come from vendors such as:

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propagated outside the next-hop AS. Not all ISPs give out their communities to the public.

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with the number of routers involved. To alleviate the problem, BGP implements two options:

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One method to address the routing table issue associated with load balancing is to deploy

2636: 992:(RFC 5065). The following discussion of basic update processing assumes a full iBGP mesh. 985: 320: 4817:, Obsolete – BGP Route Reflection – An Alternative to Full Mesh iBGP 4560:, Application of the Border Gateway Protocol in the Internet Protocol (BGP-4) using SMIv2 3295: 3176: 2623:-like overflow triggered in 2014 for those models that were not appropriately updated. 2532: 2403: 875:

Once the message has been received, the router checks the validity of the Open message.

676:). Routers on the boundary of one AS exchanging information with another AS are called 370: 588:

The current version of BGP is version 4 (BGP4), which was first published as RFC

4874: 4538: 4272:"CAT 6500 and 7600 Series Routers and Switches TCAM Allocation Adjustment Procedures" 4210:"CAT 6500 and 7600 Series Routers and Switches TCAM Allocation Adjustment Procedures" 3196: 3105: 620:

and IPv6 "address families". It is also called the Multiprotocol Extensions which is

609: 4765: 3424: 1794:

An ISP might state that any routes received from customers with following examples:

4542: 4184: 4081: 810:

If an error occurs, BGP moves to the Active state. Some reasons for the error are:

289: 3458: 2611:

by end-user networks the growth was once again superlinear by the middle of 2004.

2469:

If a route is received from a client peer, reflect to client and non-client peers.

2044:

Optional Parameters Length (8 bit): total length of the Optional parameters field.

742:

In order to make decisions in its operations with peers, a BGP peer uses a simple

711:

New routes learned from an eBGP peer are re-advertised to all iBGP and eBGP peers.

3894: 3403:

ASN 4200000000 to 4294967294 are private and 4294967295 is forbidden by RFC 7300.

3273:, the eXtensible Open Router Platform, a BSD-licensed suite of routing protocols. 2507:

These alternatives can introduce problems of their own, including the following:

2452:

A typical configuration of BGP RR deployment, as proposed by Section 6, RFC 4456.

4842: 4835: 4828: 4821: 4814: 4807: 4800: 4793: 4786: 4779: 4772: 4753: 4746: 4739: 4732: 4725: 4718: 4711: 4704: 4697: 4690: 4683: 4676: 4669: 4662: 4655: 4648: 4641: 4634: 4627: 4620: 4613: 4606: 4599: 4592: 4585: 4578: 4571: 4564: 4557: 4473: 4450: 4106: 3954: 3935: 3859: 3787: 3751: 3692: 3673: 3658: 3639: 3624: 3605: 3260: 3121: 3076: 2608: 2548: 2373: 1751: 1731: 1711: 1691: 1659: 1623: 1512: 1505:

Used to modify how a route originated within one VRF is imported into other VRFs

1492: 1472: 1453: 613: 597: 593: 589: 582: 578: 3385:

ASN 64512 to 65534 were reserved for private use and 0 and 65535 are forbidden.

2575: 4437:

https://web.archive.org/web/20110906085724/http://www.potaroo.net/tools/asn16/

4377: 3336: 3156: 1871:

10.32.37.128/26 Intra Network IP 101 ge-0/0/1.0 10.32.37.241

1868:

10.32.37.64/26 Intra Network IP 102 ge-0/0/1.0 10.32.37.241

1865:

10.32.37.0/26 Intra Network IP 101 ge-0/0/1.0 10.32.37.241

1856:

Prefix Path Route NH Metric NextHop Nexthop

1120: 1112: 714:

New routes learned from an iBGP peer are re-advertised to all eBGP peers only.

437: 4658:, BGP Route Reflection – An Alternative to Full Mesh Internal BGP (iBGP) 2053:

Type: Open Message (1) Version: 4 My AS: 64496 Hold Time: 90 BGP Identifier:

4789:, Obsolete – Application of the Border Gateway Protocol in the Internet 3248: 3242: 3232: 3228: 3207:

is often used for these different policy relationships on a running router.

3159:

use BGP internally. An example use case is the joining of a number of large

2886:

message will be sent back, depending on the configuration of AS1's routers.

110: 3195:, or a small enterprise that announces routes to an ISP but only accepts a 692:

can be interconnected through other intermediate routers. Other deployment

632:

BGP neighbors, called peers, are established by manual configuration among

4756:, Distribution of Link-State and Traffic Engineering Information Using BGP 4489:"Quick fix for an early Internet problem lives on a quarter-century later" 3191:

representing one of several smaller enterprises that are linked, by a BGP

4163: 3256: 2632: 2035:

Timeout timer, used to calculate KeepAlive messages. Default 90 seconds.

527: 4588:, NOPEER Community for Border Gateway Protocol (BGP) Route Scope Control 4321:"Internet infrastructure 'needs updating or more blackouts will happen'" 4253: 3394:

The 16-bit AS range 0 to 65535 and its reserved AS numbers are retained.

2583: 2456:

RR servers propagate routes inside the AS based on the following rules:

17: 3732: 3300: 3264: 2656: 2466:

If a route is received from a non-client peer, reflect to client peers.

697: 519: 4512: 4430: 4395: 4145: 4060: 4039: 4018: 4003: 3580: 1839:

Some routers (like Juniper) will use the Metric from OSPF to set MED.

4465: 4144:

Villamizar, Curtis; Chandra, Ravi; Govindan, Ramesh (November 1998).

3995:

BGP Route Reflection: An Alternative to Full Mesh Internal BGP (iBGP)

3946: 3684: 3650: 3616: 3481:"Network Routing with Path Vector Protocols: Theory and Applications" 1485:

At neighbor AS-peer, set LOCAL_PREF, lower to route away from source.

400: 294: 193: 173: 3835: 3155:(ISPs) to establish routing between one another. Very large private 1882:

Prefix Nexthop MED Lclpref AS path

3811: 2837:

overlaps all the other specific routes, to just store the summary,

1894:* 10.32.37.128/26 Self 101 I 1891:* 10.32.37.64/26 Self 102 I 1888:* 10.32.37.0/26 Self 101 I 1885:* 10.32.37.0/24 Self 16777215 I 664:). When it runs between different autonomous systems, it is called 549:). In contrast, the Internet application of the protocol is called 51: 4291:"Internet Touches Half Million Routes: Outages Possible Next Week" 4229:"Internet Touches Half Million Routes: Outages Possible Next Week" 4164:"RIPE Routing Working Group Recommendations On Route-flap Damping" 3977: 3914: 3711: 2750:

does not have any hosts so AS1 does not announce a specific route

2582: 2574: 2448: 421: 199: 2882:. At AS1, it will either be dropped or a destination unreachable 1932:

Marker (always: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff)

1843:

Examples of MED used with BGP when exported to BGP on Juniper SRX

4700:, BGP Support for Four-Octet Autonomous System (AS) Number Space 3428: 3341: 3286: 3270: 3128: 2628: 2421: 841:

If it is unsuccessful again, the FSM is reset to the Idle state.

617: 570: 389: 384: 354: 304: 224: 189: 3350: – Organization responsible for managing network numbering 3333: – Relaying of packets from one network segment to another 4859: 3222: 1833: 923: 721:

How routes are propagated can be controlled in detail via the

701: 209: 27:

Protocol for communicating routing information on the Internet

4185:"draft-ymbk-rfd-usable-02 - Making Route Flap Damping Usable" 4082:"Route Flap Damping Exacerbates Internet Routing Convergence" 3214:

Notable free and open-source implementations of BGP include:

4845:, Obsolete – BGP Support for Four-octet AS Number Space 2639:

among others. A number of Cisco routers commonly in use had

1032:: For each neighbor, the BGP process maintains a conceptual 1022:: For each neighbor, the BGP process maintains a conceptual 893:

The peer is listening for a Keepalive message from its peer.

4248: 4246: 3151:

BGP4 is standard for Internet routing and required of most

3067:(AS23456) is used. 32-bit ASN assignments started in 2007. 2987:, thereby reducing the number of routes AS2 stores to two ( 541:

BGP used for routing within an autonomous system is called

4865: 4831:, Obsolete – Autonomous System Confederations for BGP 4810:, Obsolete – Autonomous System Confederations for BGP 3321: – Major disruption of the Internet on April 25, 1997 2463:

Routes are never reflected to the originator of the route.

2007:

note: "Marker" and "Length" is omitted from the examples.

1859:

Type Type Type Interface Address/LSP

4120:

International Conference on Distributed Computing Systems

1986:: Type of BGP message. The following values are defined: 807:

Sends Open message to peer and changes state to OpenSent.

4693:, IPv6 Address Specific BGP Extended Community Attribute 3179:

are less likely to support BGP than devices marketed as

1836:, that they impose to send traffic to some destination. 766:

Initiates a TCP connection with its configured BGP peer.

4838:, Obsolete – Capabilities Advertisement with BGP-4 3315: – Outage affecting all Facebook operated services 3251:, a GPL routing suite supporting BGP4 (decommissioned). 2587:

Number of AS on the Internet vs number of registered AS

944: 4855: 3764:"Border Gateway Protocol (BGP) Well-known Communities" 3362: – Process of excluding certain networking routes 3327: – Standards organization overseeing IP addresses 1970:: Included for compatibility, must be set to all ones. 4803:, Obsolete – A Border Gateway Protocol 4 (BGP-4) 4782:, Obsolete – A Border Gateway Protocol 4 (BGP-4) 3127:

Multiprotocol BGP is also widely deployed in case of

2399:

BGP is "the most scalable of all routing protocols."

1862:

10.32.37.0/24 Inter Discard IP 16777215

997:

network-layer reachability information (NLRI) updates

819:

Peer address configured incorrectly on either router.

785:

Peer address configured incorrectly on either router.

4824:, Obsolete – Multiprotocol Extensions for BGP-4 3872:"Border Gateway Protocol (BGP) Extended Communities" 1115:

the route selection process moves to the next step.

4319:Garside, Juliette; Gibbs, Samuel (14 August 2014). 939:

may be too technical for most readers to understand

131: 121: 109: 99: 81: 69: 61: 4378:"TCAM — a Deeper Look and the impact of IPv6" 3934:Y. Rekhter; T. Li; S. Hares, eds. (January 2006). 3183:, but many high-end layer-3 switches can run BGP. 872:BGP FSM listens for an Open message from its peer. 822:AS number configured incorrectly on either router. 788:AS number configured incorrectly on either router. 3199:and perhaps a small number of aggregated routes. 3063:(optional transitive) and the special 16-bit ASN 2868:, it will be sent to the routers of AS1 on route 2764:. This all counts as AS1 announcing four routes. 2674:would have soon happened through natural growth. 1026:, containing the NLRI received from the neighbor. 4742:, Policy Behavior for Well-Known BGP Communities 4714:, Revised Error Handling for BGP UPDATE Messages 4513:"Zebra - GNU Project - Free Software Foundation" 1801:To Customers North America (West Coast) 3491:200 1798:To Customers North America (East Coast) 3491:100 4775:, Obsolete – Border Gateway Protocol (BGP) 801:Waits for successful TCP negotiation with peer. 4707:, IANA Registries for BGP Extended Communities 4166:. RIPE Network Coordination Centre. 2006-05-10 3368: – Routing registry for Internet networks 2595:Until late 2001, the global routing table was 2536:change may cause outages for several minutes. 1081: 1010:: routers main routing information base table. 488: 8: 3171:Routers, especially small ones intended for 1199:Accumulated Interior Gateway Protocol (AIGP) 1034:adjacent routing information base, outgoing 688:and are typically connected directly, while 648:When BGP runs between two peers in the same 37: 4749:, Dissemination of Flow Specification Rules 3356: – Internet routing security framework 1036:, containing the NLRI send to the neighbor. 1024:adjacent routing information base, incoming 769:Listens for a TCP connection from its peer. 763:Start the initialization of event triggers. 4679:, Autonomous System Confederations for BGP 4609:, Definitions of Managed Objects for BGP-4 4452:BGP Support for Four-octet AS Number Space 4435:, Geoff Huston 2011 (original archived at 2460:Routes are always reflected to eBGP peers. 2110: 1652:, by enable blackhole at neighbour AS-peer 1119:Steps to determine best path, in order of 592:in 1994, subsequently updated by RFC 495: 481: 144: 36: 30:"BGP" redirects here. For other uses, see 4464: 4111:"Timer Interaction in Route Flap Damping" 4105:Zhang, Beichuan; Pei Dan; Daniel Massey; 4002: 3945: 3683: 3649: 3615: 3579: 1605:RFC draft-agrewal-idr-accept-own-nexthop 1225:"On", skipped if ignored in configuration 967:Learn how and when to remove this message 951:, without removing the technical details. 581:in 1994, and it was improved to RFC 4721:, Advertisement of Multiple Paths in BGP 3550:"The History of Border Gateway Protocol" 3451:"BGP: Border Gateway Protocol Explained" 3018:If AS2 now wants to send data to prefix 2447: 1908: 1806:area are generally rare and accidental. 1771:Examples of common communities include: 1420: 1347:Used to ignore changes on the steps 10+ 1117: 850:A random TCP port over 1023 is not open. 816:A random TCP port over 1023 is not open. 782:A random TCP port over 1023 is not open. 696:are also possible, such as running eBGP 137: 4881:Internet properties established in 1994 4686:, Capabilities Advertisement with BGP-4 4602:, BGP Security Vulnerabilities Analysis 4449:Vohra, Quaizar; Chen, Enke (May 2007). 3416: 3378: 2889:If AS1 later decides to drop the route 2767:AS2 will see the four routes from AS1 ( 920:Router connectivity and learning routes 436: 369: 319: 154: 147: 3225:routing package for Unix-like systems. 3089:Locator/Identifier Separation Protocol 1931: 1592:RFC draft-uttaro-idr-bgp-persistence 1579:RFC draft-uttaro-idr-bgp-persistence 4595:, A Border Gateway Protocol 4 (BGP-4) 4414:"What caused today's Internet hiccup" 3607:Capabilities Advertisement with BGP-4 3344: – Traffic engineering mechanism 1684:limit to a BGP confederation boundary 949:make it understandable to non-experts 616:allows BGP4 to carry a wide range of 7: 4672:, Multiprotocol Extensions for BGP-4 4665:, Graceful Restart Mechanism for BGP 4651:, BGP Extended Communities Attribute 4637:, Experience with the BGP-4 Protocol 4581:, Route Refresh Capability for BGP-4 3993:T. Bates; et al. (April 2006). 2854:If AS2 wants to send data to prefix 1910:BGP version 4 message header format 1304:Directly connected, over indirectly 760:Refuse all incoming BGP connections. 3937:A Border Gateway Protocol 4 (BGP-4) 3788:"BGP Community Support | iFog GmbH" 3707:"BGP Best Path Selection Algorithm" 3672:E. Rosen; Y. Rekhter (April 2004). 3638:T. Bates; et al. (June 2000). 3604:R. Chandra; J. Scudder (May 2000). 3572:A Border Gateway Protocol 4 (BGP-4) 3325:Internet Assigned Numbers Authority 3050:AS number depletion and 32-bit ASNs 2237:Unrecognized Well-known Attribute. 522:and reachability information among 3962:sec. 4.1. 3728:"Understanding BGP Path Selection" 3641:Multiprotocol Extensions for BGP-4 3354:Resource Public Key Infrastructure 996: 25: 4858:(includes a dedicated section on 4728:, BGP Large Communities Attribute 4623:, BGP-4 MIB Implementation Survey 2199:Unsupported Authentication Code. 1976:: Total length of the message in 4094:from the original on 2022-10-09. 3895:IETF drafts on BGP signalled QoS 3526:from the original on 1 June 2015 2579:BGP table growth on the Internet 2517:increase of BGP convergence time 2387:Example of ROUTE-REFRESH Message 2383:, without resetting connection. 1876:showrouteadvertising-protocolbgp 1814:BGP Extended Community Attribute 1076: 928: 674:Exterior Border Gateway Protocol 662:Interior Border Gateway Protocol 551:Exterior Border Gateway Protocol 543:Interior Border Gateway Protocol 50: 4766:Selective Route Refresh for BGP 4531:"Border Gateway Protocol (BGP)" 4432:16-bit Autonomous System Report 4358:from the original on 2022-10-09 3973:"Border Gateway Protocol (BGP)" 3493:from the original on 2010-07-14 2340:Example of NOTIFICATION Message 4768:, IETF draft, November 7, 2015 4762:, IETF draft, February 3, 2017 4735:, Use of BGP Large Communities 4376:Greg Ferro (26 January 2011). 3512:Timberg, Craig (31 May 2015). 3245:systems (no longer developed). 3091:(BGP/LISP) gateways within an 2601:Classless Inter-Domain Routing 2245:Missing Well-known Attribute. 1724:limit to the autonomous system 1266:multi-exit discriminator (MED) 995:A given BGP router may accept 602:Classless Inter-Domain Routing 1: 4630:, BGP-4 Implementation Report 4227:Cowie, Jim (13 August 2014). 3046:is not in the routing table. 2478:An RR and its clients form a 1853:Topology default Route Table: 1775:local preference adjustments, 1648:To temporary protect against 772:Changes its state to Connect. 4487:Craig Timberg (2015-05-31). 3479:Sobrinho, João Luís (2003). 3455:Orbit-Computer Solutions.Com 3235:systems; and its ancestors: 3139:Another extension to BGP is 2379:Allows for soft updating of 2364:Type: KEEPALIVE Message (4) 2360:Example of KEEPALIVE Message 2285:Invalid NEXT_HOP Attribute. 2175:Unsupported Version Number. 2145:Connection Not Synchronized 1566:RFC draft-l3vpn-legacy-rtc 1336:Path that was received first 1222:Autonomous system (AS) jumps 532:path-vector routing protocol 4860:BGP & ISP Core Security 4760:BGP Custom Decision Process 4567:, BGP Communities Attribute 2325:Finite State Machine Error 1553:RFC draft-l3vpn-legacy-rtc 1540:RFC draft-l3vpn-legacy-rtc 1527:RFC draft-l3vpn-legacy-rtc 1422:Well-known BGP communities 859:Flapping network interface. 652:(AS), it is referred to as 4917: 3348:Regional Internet registry 3241:, a fork of GNU Zebra for 3153:Internet service providers 2645:content-addressable memory 2420:This approach, similar to 2293:Optional Attribute Error. 2229:Malformed Attribute List. 2222: 2219: 1954: 1917: 1548:ROUTE_FILTER_TRANSLATED_v6 1522:ROUTE_FILTER_TRANSLATED_v4 1312:IGP metric to BGP next hop 138:§ Standards documents 29: 4616:, BGP-4 Protocol Analysis 4396:"The IPv4 Depletion site" 3940:. Network Working Group. 2557:denial-of-service attacks 2332: 2324: 2316: 2269:Invalid ORIGIN Attribute 2168: 2165: 2138: 2135: 2122: 2119: 2116: 2073:Example of UPDATE Message 1960: 1957: 1923: 1920: 1827:Multi-exit discriminators 1326:interior routing protocol 1291:Local to router (Loc-RIB) 1290: 1218: 1175: 1168:Cisco-specific parameter 1082:multi-exit discriminators 1001:routing information bases 847:TCP port 179 is not open. 813:TCP port 179 is not open. 779:TCP port 179 is not open. 573:BGP was first defined in 530:. BGP is classified as a 516:exterior gateway protocol 49: 42: 4574:, BGP Route Flap Damping 4146:"BGP Route Flap Damping" 3173:small office/home office 3161:Open Shortest Path First 2261:Attribute Length Error. 2215:Unacceptable Hold Time. 2207:Authentication Failure. 1846: 1785:denial-of-service attack 1650:denial-of-service attack 1463:Reserved for private use 853:BGP configuration error. 736:multiprotocol extensions 608:to decrease the size of 4535:IOS Technology Handbook 3915:"Large BGP Communities" 3366:Routing Assets Database 3231:, a fork of Quagga for 3093:Internet exchange point 2643:, a form of high-speed 2429:single point of failure 2301:Invalid Network Field. 2253:Attribute Flags Error. 2049:Example of Open Message 1980:, including the header. 1315:"on", imported from IGP 1269:"on", imported from IGP 1095:Route selection process 508:Border Gateway Protocol 149:Internet protocol suite 38:Border Gateway Protocol 3836:"BGP Community Guides" 3263:implementation by the 2588: 2580: 2453: 2038:BGP Identifier (32bit) 1790:AS prepending options. 1781:peer type restrictions 1182:"Off", all set to 100. 730:Extensions negotiation 87:; 35 years ago 44:Communication protocol 4901:Internet architecture 4856:BGP Routing Resources 3425:"History for rfc1105" 3193:backbone of backbones 2597:growing exponentially 2586: 2578: 2553:exponentially decayed 2451: 2041:IP-address of sender. 1905:Message header format 1758:0xFFFFFF05-0xFFFFFFFF 1666:0xFFFF029B-0xFFFFFF00 1630:0xFFFF000A-0xFFFF0299 1460:0x00010000-0xFFFEFFFF 1441:0x00000000-0x0000FFFF 596:in 1995 and RFC 567:three-napkin protocol 536:network administrator 518:designed to exchange 4866:BGP table statistics 3904:, Thomas Knoll, 2008 3313:2021 Facebook outage 3282:Agilent Technologies 3134:provider edge router 2571:Routing table growth 2395:Internal scalability 2223:UPDATE Message Error 2191:Bad BGP Identifier. 2139:Message Header Error 2019:Version of BGP used. 1294:eBGP over iBGP paths 1111:As long as there is 744:finite state machine 514:) is a standardized 32:BGP (disambiguation) 4551:Standards documents 4493:The Washington Post 3560:on 29 October 2020. 3519:The Washington Post 2678:Route summarization 2539:A feature known as 2514:sub-optimal routing 2317:Hold Timer Expired 2309:Malformed AS_PATH. 2153:Bad Message Length 2113: 1911: 1721:NO_EXPORT_SUBCONFED 1704:limit to a BGP peer 1423: 1373:Cluster list length 1124: 982:grows quadratically 856:Network congestion. 77:routing information 39: 4891:Internet protocols 4886:Internet Standards 4239:on 13 August 2014. 3900:2009-02-23 at the 2660:Autonomous Systems 2589: 2581: 2541:route flap damping 2454: 2169:OPEN Message Error 2111: 1909: 1600:accept-own-nexthop 1421: 1118: 1088:autonomous systems 990:BGP confederations 604:(CIDR) and use of 524:autonomous systems 4896:Routing protocols 4400:ipv4depletion.com 4351:. www.nanog.org. 4152:. Tools.ietf.org. 4087:. November 1998. 3812:"BGP communities" 3331:Packet forwarding 3291:network simulator 3141:multipath routing 2605:route aggregation 2511:route oscillation 2337: 2336: 2277:AS Routing Loop. 2161:Bad Message Type 2032:Hold Time (16bit) 2027:autonomous system 2001:Route-Refresh (5) 1964: 1963: 1851:runshowospfroute 1769: 1768: 1482:GRACEFUL_SHUTDOWN 1401: 1400: 977: 976: 969: 905:Established State 888:OpenConfirm State 650:autonomous system 622:Multiprotocol BGP 606:route aggregation 505: 504: 156:Application layer 143: 142: 116:Application layer 85:June 1, 1989 75:Internet Protocol 56:BGP state machine 16:(Redirected from 4908: 4546: 4541:, archived from 4517: 4516: 4509: 4503: 4502: 4500: 4499: 4484: 4478: 4477: 4468: 4466:10.17487/RFC4893 4446: 4440: 4428: 4422: 4421: 4410: 4404: 4403: 4392: 4386: 4385: 4373: 4367: 4366: 4364: 4363: 4357: 4350: 4342: 4336: 4335: 4333: 4331: 4316: 4310: 4309: 4307: 4306: 4297:. Archived from 4286: 4280: 4279: 4268: 4262: 4261: 4250: 4241: 4240: 4235:. Archived from 4224: 4218: 4217: 4206: 4200: 4199: 4197: 4196: 4191:. Tools.ietf.org 4189:Ietf Datatracker 4181: 4175: 4174: 4172: 4171: 4160: 4154: 4153: 4150:Ietf Datatracker 4141: 4135: 4134: 4128: 4127: 4115: 4102: 4096: 4095: 4093: 4086: 4078: 4072: 4071: 4069: 4068: 4057: 4051: 4050: 4048: 4047: 4036: 4030: 4029: 4027: 4026: 4015: 4009: 4008: 4006: 3990: 3984: 3983: 3969: 3963: 3958: 3949: 3947:10.17487/RFC4271 3931: 3925: 3924: 3922: 3921: 3911: 3905: 3892: 3886: 3885: 3883: 3882: 3868: 3862: 3853: 3847: 3846: 3844: 3842: 3832: 3826: 3825: 3823: 3822: 3808: 3802: 3801: 3799: 3798: 3784: 3778: 3777: 3775: 3774: 3760: 3754: 3745: 3739: 3738: 3724: 3718: 3717: 3703: 3697: 3696: 3687: 3685:10.17487/RFC2547 3669: 3663: 3662: 3653: 3651:10.17487/RFC2858 3635: 3629: 3628: 3619: 3617:10.17487/RFC2842 3601: 3595: 3592: 3586: 3585: 3583: 3568: 3562: 3561: 3556:. Archived from 3554:blog.datapath.io 3546: 3540: 3539: 3533: 3531: 3509: 3503: 3502: 3500: 3498: 3492: 3485: 3476: 3470: 3469: 3467: 3466: 3457:. Archived from 3447: 3441: 3440: 3438: 3436: 3421: 3404: 3401: 3395: 3392: 3386: 3383: 3319:AS 7007 incident 3189:confederation-AS 3177:layer-3 switches 3044: 3043: 3040: 3037: 3030: 3029: 3026: 3023: 3013: 3012: 3009: 3006: 2999: 2998: 2995: 2992: 2985: 2984: 2981: 2978: 2971: 2970: 2967: 2964: 2957: 2956: 2953: 2950: 2943: 2942: 2939: 2936: 2929: 2928: 2925: 2922: 2915: 2914: 2911: 2908: 2901: 2900: 2897: 2894: 2880: 2879: 2876: 2873: 2866: 2865: 2862: 2859: 2849: 2848: 2845: 2842: 2835: 2834: 2831: 2828: 2821: 2820: 2817: 2814: 2807: 2806: 2803: 2800: 2793: 2792: 2789: 2786: 2779: 2778: 2775: 2772: 2762: 2761: 2758: 2755: 2748: 2747: 2744: 2741: 2734: 2733: 2730: 2727: 2720: 2719: 2716: 2713: 2706: 2705: 2702: 2699: 2692: 2691: 2688: 2685: 2671: 2670: 2667: 2649:spillover effect 2434: 2415:Route reflectors 2410:Route reflectors 2382: 2355: 2114: 2098: 2097: 2091: 2090: 2084: 2083: 2059: 2058: 1995:Notification (3) 1912: 1895: 1892: 1889: 1886: 1883: 1879: 1875: 1872: 1869: 1866: 1863: 1860: 1857: 1854: 1850: 1424: 1391:Neighbor address 1179:Local preference 1125: 1064: 1060: 1056: 1052: 1048: 1044: 1031: 1021: 1015: 1009: 986:route reflectors 972: 965: 961: 958: 952: 932: 931: 924: 497: 490: 483: 145: 95: 93: 88: 54: 40: 21: 4916: 4915: 4911: 4910: 4909: 4907: 4906: 4905: 4871: 4870: 4852: 4553: 4529: 4526: 4524:Further reading 4521: 4520: 4511: 4510: 4506: 4497: 4495: 4486: 4485: 4481: 4448: 4447: 4443: 4429: 4425: 4412: 4411: 4407: 4394: 4393: 4389: 4375: 4374: 4370: 4361: 4359: 4355: 4348: 4344: 4343: 4339: 4329: 4327: 4318: 4317: 4313: 4304: 4302: 4288: 4287: 4283: 4278:. 9 March 2015. 4270: 4269: 4265: 4252: 4251: 4244: 4226: 4225: 4221: 4208: 4207: 4203: 4194: 4192: 4183: 4182: 4178: 4169: 4167: 4162: 4161: 4157: 4143: 4142: 4138: 4125: 4123: 4113: 4104: 4103: 4099: 4091: 4084: 4080: 4079: 4075: 4066: 4064: 4059: 4058: 4054: 4045: 4043: 4038: 4037: 4033: 4024: 4022: 4017: 4016: 4012: 3992: 3991: 3987: 3971: 3970: 3966: 3960:Draft Standard. 3933: 3932: 3928: 3919: 3917: 3913: 3912: 3908: 3902:Wayback Machine 3893: 3889: 3880: 3878: 3870: 3869: 3865: 3854: 3850: 3840: 3838: 3834: 3833: 3829: 3820: 3818: 3810: 3809: 3805: 3796: 3794: 3786: 3785: 3781: 3772: 3770: 3762: 3761: 3757: 3746: 3742: 3726: 3725: 3721: 3705: 3704: 3700: 3671: 3670: 3666: 3637: 3636: 3632: 3603: 3602: 3598: 3593: 3589: 3570: 3569: 3565: 3548: 3547: 3543: 3529: 3527: 3511: 3510: 3506: 3496: 3494: 3490: 3483: 3478: 3477: 3473: 3464: 3462: 3449: 3448: 3444: 3434: 3432: 3423: 3422: 3418: 3413: 3408: 3407: 3402: 3398: 3393: 3389: 3384: 3380: 3375: 3360:Route filtering 3309: 3169: 3167:Implementations 3149: 3114: 3101: 3073: 3052: 3041: 3038: 3035: 3034: 3027: 3024: 3021: 3020: 3010: 3007: 3004: 3003: 2996: 2993: 2990: 2989: 2982: 2979: 2976: 2975: 2968: 2965: 2962: 2961: 2954: 2951: 2948: 2947: 2940: 2937: 2934: 2933: 2926: 2923: 2920: 2919: 2912: 2909: 2906: 2905: 2898: 2895: 2892: 2891: 2877: 2874: 2871: 2870: 2863: 2860: 2857: 2856: 2846: 2843: 2840: 2839: 2832: 2829: 2826: 2825: 2818: 2815: 2812: 2811: 2804: 2801: 2798: 2797: 2790: 2787: 2784: 2783: 2776: 2773: 2770: 2769: 2759: 2756: 2753: 2752: 2745: 2742: 2739: 2738: 2731: 2728: 2725: 2724: 2717: 2714: 2711: 2710: 2703: 2700: 2697: 2696: 2689: 2686: 2683: 2682: 2668: 2665: 2664: 2637:Microsoft Azure 2617: 2573: 2528: 2493: 2476: 2446: 2433:11 × 2 − 2 = 20 2432: 2412: 2397: 2392: 2380: 2370: 2365: 2353: 2350: 2345: 2105: 2100: 2095: 2094: 2088: 2087: 2081: 2080: 2067: 2062: 2056: 2055: 2013: 1907: 1902: 1897: 1896: 1893: 1890: 1887: 1884: 1881: 1877: 1873: 1870: 1867: 1864: 1861: 1858: 1855: 1852: 1848: 1832:presence at an 1829: 1816: 1561:ROUTE_FILTER_v6 1535:ROUTE_FILTER_v4 1427:Attribute value 1415: 1279: 1275:MULTI_EXIT_DISC 1258:2 = Incomplete 1257: 1255: 1154:Local to router 1097: 1062: 1058: 1054: 1050: 1046: 1042: 1029: 1019: 1013: 1007: 988:(RFC 4456) and 973: 962: 956: 953: 945:help improve it 942: 933: 929: 922: 732: 630: 563: 501: 321:Transport layer 91: 89: 86: 57: 35: 28: 23: 22: 15: 12: 11: 5: 4914: 4912: 4904: 4903: 4898: 4893: 4888: 4883: 4873: 4872: 4869: 4868: 4863: 4851: 4850:External links 4848: 4847: 4846: 4839: 4832: 4825: 4818: 4811: 4804: 4797: 4790: 4783: 4776: 4769: 4763: 4757: 4750: 4743: 4736: 4729: 4722: 4715: 4708: 4701: 4694: 4687: 4680: 4673: 4666: 4659: 4652: 4645: 4638: 4631: 4624: 4617: 4610: 4603: 4596: 4589: 4582: 4575: 4568: 4561: 4552: 4549: 4548: 4547: 4525: 4522: 4519: 4518: 4504: 4479: 4441: 4423: 4405: 4387: 4368: 4337: 4311: 4281: 4263: 4242: 4219: 4201: 4176: 4155: 4136: 4097: 4073: 4063:. www.ietf.org 4052: 4042:. www.ietf.org 4031: 4021:. www.ietf.org 4010: 3985: 3964: 3926: 3906: 3887: 3863: 3848: 3827: 3803: 3779: 3755: 3740: 3719: 3698: 3664: 3630: 3596: 3587: 3563: 3541: 3504: 3471: 3442: 3415: 3414: 3412: 3409: 3406: 3405: 3396: 3387: 3377: 3376: 3374: 3371: 3370: 3369: 3363: 3357: 3351: 3345: 3339: 3334: 3328: 3322: 3316: 3308: 3305: 3304: 3303: 3298: 3293: 3284: 3275: 3274: 3268: 3254: 3253: 3252: 3246: 3226: 3168: 3165: 3148: 3145: 3113: 3110: 3100: 3097: 3072: 3071:Load balancing 3069: 3051: 3048: 2616: 2613: 2572: 2569: 2533:route flapping 2527: 2524: 2519: 2518: 2515: 2512: 2492: 2489: 2475: 2472: 2471: 2470: 2467: 2464: 2461: 2445: 2442: 2411: 2408: 2396: 2393: 2390: 2372:Defined in RFC 2369: 2366: 2363: 2349: 2346: 2343: 2335: 2334: 2331: 2327: 2326: 2323: 2319: 2318: 2315: 2311: 2310: 2307: 2303: 2302: 2299: 2295: 2294: 2291: 2287: 2286: 2283: 2279: 2278: 2275: 2271: 2270: 2267: 2263: 2262: 2259: 2255: 2254: 2251: 2247: 2246: 2243: 2239: 2238: 2235: 2231: 2230: 2227: 2224: 2221: 2217: 2216: 2213: 2209: 2208: 2205: 2201: 2200: 2197: 2193: 2192: 2189: 2185: 2184: 2181: 2177: 2176: 2173: 2170: 2167: 2163: 2162: 2159: 2155: 2154: 2151: 2147: 2146: 2143: 2140: 2137: 2133: 2132: 2129: 2125: 2124: 2121: 2118: 2104: 2101: 2076: 2066: 2063: 2052: 2046: 2045: 2042: 2039: 2036: 2033: 2030: 2023: 2020: 2017: 2016:Version (8bit) 2012: 2009: 2005: 2004: 2003: 2002: 1999: 1996: 1993: 1990: 1981: 1971: 1962: 1961: 1959: 1956: 1953: 1949: 1948: 1944: 1943: 1939: 1938: 1934: 1933: 1930: 1926: 1925: 1922: 1919: 1916: 1906: 1903: 1901: 1898: 1847: 1828: 1825: 1815: 1812: 1803: 1802: 1799: 1792: 1791: 1788: 1787:identification 1782: 1779: 1776: 1767: 1766: 1764: 1762: 1759: 1755: 1754: 1745: 1742: 1739: 1735: 1734: 1725: 1722: 1719: 1715: 1714: 1705: 1702: 1699: 1695: 1694: 1685: 1682: 1679: 1675: 1674: 1672: 1670: 1667: 1663: 1662: 1653: 1646: 1643: 1639: 1638: 1636: 1634: 1631: 1627: 1626: 1617: 1614: 1611: 1607: 1606: 1603: 1601: 1598: 1594: 1593: 1590: 1588: 1585: 1581: 1580: 1577: 1575: 1572: 1568: 1567: 1564: 1562: 1559: 1555: 1554: 1551: 1549: 1546: 1542: 1541: 1538: 1536: 1533: 1529: 1528: 1525: 1523: 1520: 1516: 1515: 1506: 1503: 1500: 1496: 1495: 1486: 1483: 1480: 1476: 1475: 1466: 1464: 1461: 1457: 1456: 1447: 1445: 1442: 1438: 1437: 1434: 1431: 1428: 1414: 1411: 1399: 1398: 1395: 1392: 1389: 1385: 1384: 1382: 1380: 1377: 1374: 1371: 1367: 1366: 1364: 1362: 1359: 1356: 1353: 1349: 1348: 1345: 1343: 1340: 1337: 1334: 1330: 1329: 1321: 1319: 1316: 1313: 1310: 1306: 1305: 1302: 1300: 1298: 1295: 1292: 1289: 1285: 1284: 1276: 1273: 1270: 1267: 1264: 1260: 1259: 1252: 1249: 1246: 1243: 1240: 1236: 1235: 1232: 1229: 1226: 1223: 1220: 1219:External to AS 1217: 1213: 1212: 1209: 1206: 1203: 1200: 1197: 1193: 1192: 1189: 1186: 1183: 1180: 1177: 1176:Internal to AS 1174: 1170: 1169: 1166: 1164: 1161: 1158: 1155: 1152: 1148: 1147: 1144: 1141: 1138: 1135: 1132: 1129: 1096: 1093: 1092: 1091: 1085: 1079: 1061:, and whether 1038: 1037: 1027: 1017: 1011: 975: 974: 936: 934: 927: 921: 918: 917: 916: 915: 914: 911: 902: 901: 900: 897: 894: 885: 884: 883: 880: 876: 873: 867:OpenSent State 864: 863: 862: 861: 860: 857: 854: 851: 848: 842: 839: 836: 827: 826: 825: 824: 823: 820: 817: 814: 808: 805: 802: 793: 792: 791: 790: 789: 786: 783: 780: 773: 770: 767: 764: 761: 731: 728: 716: 715: 712: 629: 626: 610:routing tables 562: 559: 503: 502: 500: 499: 492: 485: 477: 474: 473: 472: 471: 464: 459: 454: 449: 441: 440: 434: 433: 432: 431: 424: 419: 414: 409: 404: 394: 393: 392: 387: 374: 373: 371:Internet layer 367: 366: 365: 364: 357: 352: 347: 342: 337: 332: 324: 323: 317: 316: 315: 314: 307: 302: 297: 292: 287: 282: 277: 272: 267: 262: 257: 252: 247: 242: 237: 232: 227: 222: 217: 212: 207: 202: 197: 187: 182: 177: 167: 159: 158: 152: 151: 141: 140: 135: 129: 128: 125: 119: 118: 113: 107: 106: 101: 97: 96: 83: 79: 78: 71: 67: 66: 63: 59: 58: 55: 47: 46: 26: 24: 14: 13: 10: 9: 6: 4: 3: 2: 4913: 4902: 4899: 4897: 4894: 4892: 4889: 4887: 4884: 4882: 4879: 4878: 4876: 4867: 4864: 4861: 4857: 4854: 4853: 4849: 4844: 4840: 4837: 4833: 4830: 4826: 4823: 4819: 4816: 4812: 4809: 4805: 4802: 4798: 4795: 4791: 4788: 4784: 4781: 4777: 4774: 4770: 4767: 4764: 4761: 4758: 4755: 4751: 4748: 4744: 4741: 4737: 4734: 4730: 4727: 4723: 4720: 4716: 4713: 4709: 4706: 4702: 4699: 4695: 4692: 4688: 4685: 4681: 4678: 4674: 4671: 4667: 4664: 4660: 4657: 4653: 4650: 4646: 4643: 4639: 4636: 4632: 4629: 4625: 4622: 4618: 4615: 4611: 4608: 4604: 4601: 4597: 4594: 4590: 4587: 4583: 4580: 4576: 4573: 4569: 4566: 4562: 4559: 4555: 4554: 4550: 4545:on 2011-07-08 4544: 4540: 4539:Cisco Systems 4536: 4532: 4528: 4527: 4523: 4514: 4508: 4505: 4494: 4490: 4483: 4480: 4475: 4472: 4467: 4462: 4458: 4454: 4453: 4445: 4442: 4438: 4434: 4433: 4427: 4424: 4419: 4415: 4409: 4406: 4401: 4397: 4391: 4388: 4383: 4379: 4372: 4369: 4354: 4347: 4341: 4338: 4326: 4322: 4315: 4312: 4301:on 2014-08-17 4300: 4296: 4292: 4285: 4282: 4277: 4273: 4267: 4264: 4259: 4255: 4254:"BGP Reports" 4249: 4247: 4243: 4238: 4234: 4230: 4223: 4220: 4215: 4211: 4205: 4202: 4190: 4186: 4180: 4177: 4165: 4159: 4156: 4151: 4147: 4140: 4137: 4133: 4122: 4121: 4112: 4109:(June 2005). 4108: 4101: 4098: 4090: 4083: 4077: 4074: 4062: 4056: 4053: 4041: 4035: 4032: 4020: 4014: 4011: 4005: 4000: 3996: 3989: 3986: 3981: 3979: 3974: 3968: 3965: 3961: 3956: 3953: 3948: 3943: 3939: 3938: 3930: 3927: 3916: 3910: 3907: 3903: 3899: 3896: 3891: 3888: 3877: 3873: 3867: 3864: 3861: 3857: 3852: 3849: 3837: 3831: 3828: 3817: 3813: 3807: 3804: 3793: 3789: 3783: 3780: 3769: 3765: 3759: 3756: 3753: 3749: 3744: 3741: 3736: 3734: 3729: 3723: 3720: 3715: 3713: 3708: 3702: 3699: 3694: 3691: 3686: 3681: 3677: 3676: 3675:BGP/MPLS VPNs 3668: 3665: 3660: 3657: 3652: 3647: 3643: 3642: 3634: 3631: 3626: 3623: 3618: 3613: 3609: 3608: 3600: 3597: 3591: 3588: 3582: 3577: 3573: 3567: 3564: 3559: 3555: 3551: 3545: 3542: 3538: 3525: 3521: 3520: 3515: 3508: 3505: 3489: 3482: 3475: 3472: 3461:on 2013-09-28 3460: 3456: 3452: 3446: 3443: 3430: 3426: 3420: 3417: 3410: 3400: 3397: 3391: 3388: 3382: 3379: 3372: 3367: 3364: 3361: 3358: 3355: 3352: 3349: 3346: 3343: 3340: 3338: 3335: 3332: 3329: 3326: 3323: 3320: 3317: 3314: 3311: 3310: 3306: 3302: 3299: 3297: 3294: 3292: 3288: 3285: 3283: 3280: 3279: 3278: 3272: 3269: 3266: 3262: 3258: 3255: 3250: 3247: 3244: 3240: 3237: 3236: 3234: 3230: 3227: 3224: 3220: 3217: 3216: 3215: 3212: 3208: 3206: 3200: 3198: 3197:default route 3194: 3190: 3184: 3182: 3178: 3174: 3166: 3164: 3162: 3158: 3154: 3146: 3144: 3142: 3137: 3136:for routing. 3135: 3130: 3125: 3123: 3119: 3111: 3109: 3107: 3106:BGP hijacking 3098: 3096: 3094: 3090: 3085: 3081: 3078: 3070: 3068: 3066: 3062: 3056: 3049: 3047: 3045: 3031: 3016: 3014: 3000: 2986: 2972: 2958: 2944: 2930: 2916: 2902: 2887: 2885: 2881: 2867: 2852: 2850: 2836: 2822: 2808: 2794: 2780: 2765: 2763: 2749: 2736:. The prefix 2735: 2721: 2707: 2693: 2679: 2675: 2672: 2661: 2658: 2653: 2650: 2646: 2642: 2638: 2634: 2630: 2624: 2622: 2614: 2612: 2610: 2606: 2602: 2598: 2593: 2585: 2577: 2570: 2568: 2564: 2560: 2558: 2554: 2550: 2546: 2542: 2537: 2534: 2525: 2523: 2516: 2513: 2510: 2509: 2508: 2505: 2501: 2497: 2491:Confederation 2490: 2488: 2485: 2481: 2473: 2468: 2465: 2462: 2459: 2458: 2457: 2450: 2443: 2441: 2437: 2430: 2425: 2423: 2418: 2416: 2409: 2407: 2405: 2400: 2394: 2389: 2388: 2384: 2377: 2375: 2368:Route-Refresh 2367: 2362: 2361: 2357: 2347: 2342: 2341: 2329: 2328: 2321: 2320: 2313: 2312: 2308: 2305: 2304: 2300: 2297: 2296: 2292: 2289: 2288: 2284: 2281: 2280: 2276: 2273: 2272: 2268: 2265: 2264: 2260: 2257: 2256: 2252: 2249: 2248: 2244: 2241: 2240: 2236: 2233: 2232: 2228: 2225: 2218: 2214: 2211: 2210: 2206: 2203: 2202: 2198: 2195: 2194: 2190: 2187: 2186: 2183:Bad Peer AS. 2182: 2179: 2178: 2174: 2171: 2164: 2160: 2157: 2156: 2152: 2149: 2148: 2144: 2141: 2134: 2130: 2127: 2126: 2115: 2109: 2102: 2099: 2096:192.0.2.64/27 2092: 2089:192.0.2.32/27 2085: 2075: 2074: 2070: 2065:Update Packet 2064: 2060: 2051: 2050: 2043: 2040: 2037: 2034: 2031: 2028: 2024: 2022:My AS (16bit) 2021: 2018: 2015: 2014: 2010: 2008: 2000: 1998:KeepAlive (4) 1997: 1994: 1991: 1988: 1987: 1985: 1982: 1979: 1975: 1972: 1969: 1966: 1965: 1951: 1950: 1946: 1945: 1941: 1940: 1936: 1935: 1928: 1927: 1914: 1913: 1904: 1900:Packet format 1899: 1845: 1844: 1840: 1837: 1835: 1826: 1824: 1820: 1813: 1811: 1807: 1800: 1797: 1796: 1795: 1789: 1786: 1783: 1780: 1777: 1774: 1773: 1772: 1765: 1763: 1760: 1757: 1756: 1753: 1749: 1746: 1743: 1740: 1737: 1736: 1733: 1729: 1726: 1723: 1720: 1717: 1716: 1713: 1709: 1706: 1703: 1700: 1697: 1696: 1693: 1689: 1686: 1683: 1680: 1677: 1676: 1673: 1671: 1668: 1665: 1664: 1661: 1657: 1654: 1651: 1647: 1644: 1641: 1640: 1637: 1635: 1632: 1629: 1628: 1625: 1621: 1618: 1615: 1612: 1609: 1608: 1604: 1602: 1599: 1596: 1595: 1591: 1589: 1586: 1583: 1582: 1578: 1576: 1573: 1570: 1569: 1565: 1563: 1560: 1557: 1556: 1552: 1550: 1547: 1544: 1543: 1539: 1537: 1534: 1531: 1530: 1526: 1524: 1521: 1518: 1517: 1514: 1510: 1507: 1504: 1501: 1498: 1497: 1494: 1490: 1487: 1484: 1481: 1478: 1477: 1474: 1470: 1467: 1465: 1462: 1459: 1458: 1455: 1451: 1448: 1446: 1443: 1440: 1439: 1435: 1432: 1429: 1426: 1425: 1419: 1412: 1410: 1407: 1396: 1393: 1390: 1387: 1386: 1383: 1381: 1378: 1375: 1372: 1369: 1368: 1365: 1363: 1360: 1357: 1354: 1351: 1350: 1346: 1344: 1341: 1338: 1335: 1332: 1331: 1327: 1322: 1320: 1317: 1314: 1311: 1308: 1307: 1303: 1301: 1299: 1296: 1293: 1287: 1286: 1283: 1277: 1274: 1271: 1268: 1265: 1262: 1261: 1253: 1250: 1247: 1244: 1241: 1238: 1237: 1233: 1230: 1227: 1224: 1221: 1215: 1214: 1210: 1207: 1204: 1201: 1198: 1195: 1194: 1190: 1187: 1184: 1181: 1178: 1172: 1171: 1167: 1165: 1162: 1159: 1156: 1153: 1150: 1149: 1145: 1142: 1139: 1136: 1133: 1130: 1127: 1126: 1122: 1116: 1114: 1109: 1105: 1101: 1094: 1089: 1086: 1083: 1080: 1078: 1075: 1074: 1073: 1070: 1066: 1035: 1028: 1025: 1018: 1012: 1006: 1005: 1004: 1002: 998: 993: 991: 987: 983: 971: 968: 960: 950: 946: 940: 937:This section 935: 926: 925: 919: 912: 909: 908: 906: 903: 898: 895: 892: 891: 889: 886: 881: 877: 874: 871: 870: 868: 865: 858: 855: 852: 849: 846: 845: 843: 840: 837: 834: 833: 831: 828: 821: 818: 815: 812: 811: 809: 806: 803: 800: 799: 797: 796:Connect State 794: 787: 784: 781: 778: 777: 774: 771: 768: 765: 762: 759: 758: 756: 753: 752: 751: 747: 745: 740: 737: 729: 727: 724: 719: 713: 710: 709: 708: 705: 703: 699: 695: 691: 687: 683: 679: 675: 671: 667: 663: 659: 655: 651: 646: 643: 639: 635: 627: 625: 623: 619: 615: 611: 607: 603: 599: 595: 591: 586: 584: 580: 576: 572: 568: 560: 558: 556: 552: 548: 544: 539: 537: 533: 529: 525: 521: 517: 513: 509: 498: 493: 491: 486: 484: 479: 478: 476: 475: 470: 469: 465: 463: 460: 458: 455: 453: 450: 448: 445: 444: 443: 442: 439: 435: 430: 429: 425: 423: 420: 418: 415: 413: 410: 408: 405: 402: 398: 395: 391: 388: 386: 383: 382: 381: 378: 377: 376: 375: 372: 368: 363: 362: 358: 356: 353: 351: 348: 346: 343: 341: 338: 336: 333: 331: 328: 327: 326: 325: 322: 318: 313: 312: 308: 306: 303: 301: 298: 296: 293: 291: 288: 286: 283: 281: 278: 276: 273: 271: 268: 266: 263: 261: 258: 256: 253: 251: 248: 246: 243: 241: 238: 236: 233: 231: 228: 226: 223: 221: 218: 216: 213: 211: 208: 206: 203: 201: 198: 195: 191: 188: 186: 183: 181: 178: 175: 171: 168: 166: 163: 162: 161: 160: 157: 153: 150: 146: 139: 136: 134: 130: 126: 124: 120: 117: 114: 112: 108: 105: 102: 98: 84: 80: 76: 72: 68: 64: 60: 53: 48: 45: 41: 33: 19: 4543:the original 4534: 4507: 4496:. Retrieved 4492: 4482: 4451: 4444: 4431: 4426: 4417: 4408: 4399: 4390: 4382:EtherealMind 4381: 4371: 4360:. Retrieved 4346:"BOF report" 4340: 4328:. Retrieved 4325:The Guardian 4324: 4314: 4303:. Retrieved 4299:the original 4295:Dyn Research 4294: 4284: 4275: 4266: 4257: 4237:the original 4232: 4222: 4213: 4204: 4193:. Retrieved 4188: 4179: 4168:. Retrieved 4158: 4149: 4139: 4130: 4124:. Retrieved 4117: 4100: 4076: 4065:. Retrieved 4055: 4044:. Retrieved 4034: 4023:. Retrieved 4013: 3994: 3988: 3976: 3967: 3959: 3936: 3929: 3918:. Retrieved 3909: 3890: 3879:. Retrieved 3876:www.iana.org 3875: 3866: 3851: 3839:. Retrieved 3830: 3819:. Retrieved 3815: 3806: 3795:. Retrieved 3791: 3782: 3771:. Retrieved 3768:www.iana.org 3767: 3758: 3743: 3731: 3722: 3710: 3701: 3674: 3667: 3640: 3633: 3606: 3599: 3590: 3571: 3566: 3558:the original 3553: 3544: 3535: 3528:. Retrieved 3517: 3507: 3495:. Retrieved 3474: 3463:. Retrieved 3459:the original 3454: 3445: 3433:. Retrieved 3419: 3399: 3390: 3381: 3289:open source 3276: 3261:BSD-licensed 3213: 3209: 3204: 3201: 3185: 3170: 3150: 3138: 3126: 3115: 3102: 3086: 3082: 3074: 3064: 3060: 3057: 3053: 3036:172.16.192.0 3033: 3022:172.16.192.0 3019: 3017: 3005:172.16.128.0 3002: 2988: 2974: 2960: 2946: 2935:172.16.128.0 2932: 2918: 2904: 2890: 2888: 2869: 2858:172.16.192.0 2855: 2853: 2838: 2824: 2813:172.16.128.0 2810: 2796: 2782: 2768: 2766: 2754:172.16.192.0 2751: 2740:172.16.192.0 2737: 2726:172.16.128.0 2723: 2709: 2695: 2681: 2676: 2663: 2654: 2625: 2618: 2594: 2590: 2565: 2561: 2540: 2538: 2529: 2520: 2506: 2502: 2498: 2494: 2483: 2479: 2477: 2455: 2438: 2426: 2419: 2414: 2413: 2401: 2398: 2386: 2385: 2378: 2371: 2359: 2358: 2351: 2339: 2338: 2112:Error Codes 2106: 2103:Notification 2093: 2086: 2082:192.0.2.0/27 2079: 2072: 2071: 2068: 2054: 2048: 2047: 2006: 1983: 1973: 1967: 1842: 1841: 1838: 1830: 1821: 1817: 1808: 1804: 1793: 1770: 1701:NO_ADVERTISE 1416: 1405: 1402: 1379:Lowest 1361:Lowest 1318:Lowest 1280: 1272:Lowest 1248:Lowest 1228:Lowest 1205:Lowest 1157:local Weight 1110: 1106: 1102: 1098: 1071: 1067: 1039: 1033: 1023: 994: 978: 963: 954: 938: 904: 887: 866: 830:Active State 829: 795: 754: 748: 741: 733: 722: 720: 717: 706: 689: 685: 682:edge routers 681: 677: 673: 669: 666:External BGP 665: 661: 657: 654:Internal BGP 653: 647: 636:to create a 631: 587: 566: 564: 554: 550: 546: 542: 540: 526:(AS) on the 511: 507: 506: 467: 427: 360: 310: 164: 82:Introduction 62:Abbreviation 4289:Jim Cowie. 4258:potaroo.net 4233:renesys.com 4107:Lixia Zhang 3431:. June 1989 3157:IP networks 3077:multi-homed 2963:172.16.64.0 2921:172.16.64.0 2799:172.16.64.0 2712:172.16.64.0 2609:multihoming 2603:(CIDR) and 2427:An RR is a 2057:192.0.2.254 2011:Open Packet 1915:bit offset 1880:.32.94.169 1433:Description 1413:Communities 1242:origin type 1077:Communities 1047:Adj-RIB-Out 1030:Adj-RIB-Out 640:session on 612:. RFC 4875:Categories 4498:2015-06-01 4418:bgpmon.net 4362:2019-12-17 4305:2015-01-02 4195:2013-12-04 4170:2013-12-04 4126:2006-09-26 4118:IEEE 25th 4067:2019-12-17 4046:2019-12-17 4025:2019-12-17 3920:2021-11-27 3881:2022-12-04 3821:2022-12-04 3797:2022-12-04 3773:2022-12-04 3465:2013-10-08 3435:1 December 3411:References 3337:Private IP 3112:Extensions 2991:172.16.0.0 2977:172.16.0.0 2949:172.16.0.0 2907:172.16.0.0 2903:, leaving 2893:172.16.0.0 2872:172.16.0.0 2841:172.16.0.0 2827:172.16.0.0 2785:172.16.0.0 2771:172.16.0.0 2698:172.16.0.0 2684:172.16.0.0 2484:cluster ID 2381:Adj-RIB-in 2117:Error Code 1992:Update (2) 1778:geographic 1761:Unassigned 1738:0xFFFFFF04 1718:0xFFFFFF03 1698:0xFFFFFF02 1678:0xFFFFFF01 1669:Unassigned 1642:0xFFFF029A 1633:Unassigned 1613:Standby PE 1610:0xFFFF0009 1597:0xFFFF0008 1584:0xFFFF0007 1574:LLGR_STALE 1571:0xFFFF0006 1558:0xFFFF0005 1545:0xFFFF0004 1532:0xFFFF0003 1519:0xFFFF0002 1502:ACCEPT_OWN 1499:0xFFFF0001 1479:0xFFFF0000 1436:Reference 1188:LOCAL_PREF 1121:tiebreaker 1113:tiebreaker 1043:Adj-RIB-In 1020:Adj-RIB-In 957:April 2021 755:Idle State 723:route-maps 694:topologies 690:iBGP peers 686:eBGP peers 684:or simply 624:(MP-BGP). 438:Link layer 92:1989-06-01 4841:RFC 4834:RFC 4827:RFC 4820:RFC 4813:RFC 4806:RFC 4799:RFC 4792:RFC 4785:RFC 4778:RFC 4771:RFC 4752:RFC 4745:RFC 4738:RFC 4731:RFC 4724:RFC 4717:RFC 4710:RFC 4703:RFC 4696:RFC 4689:RFC 4682:RFC 4675:RFC 4668:RFC 4661:RFC 4654:RFC 4647:RFC 4640:RFC 4633:RFC 4626:RFC 4619:RFC 4612:RFC 4605:RFC 4598:RFC 4591:RFC 4584:RFC 4577:RFC 4570:RFC 4563:RFC 4556:RFC 3530:4 January 3497:March 16, 3249:GNU Zebra 3243:Unix-like 3233:Unix-like 3229:FRRouting 2526:Stability 2404:full mesh 2348:KeepAlive 2123:subcodes 1681:NO_EXPORT 1645:BLACKHOLE 1430:Attribute 1406:community 1355:Router ID 1143:BGP field 1140:Preferred 879:occurred. 700:inside a 628:Operation 585:in 1998. 111:OSI layer 73:exchange 4353:Archived 4089:Archived 3898:Archived 3841:13 April 3816:retn.net 3594:RFC 4274 3524:Archived 3488:Archived 3307:See also 3257:OpenBGPD 3099:Security 3065:AS_TRANS 3061:AS4_PATH 2633:LastPass 2615:512k day 2354:holdtime 2025:Senders 1989:Open (1) 1444:Reserved 1211:rfc7311 1055:Adj-RIBs 1049:and the 528:Internet 100:Based on 18:512k day 3792:ifog.ch 3733:Juniper 3301:Spirent 3265:OpenBSD 3181:routers 2657:Verizon 2480:cluster 2474:Cluster 2029:number. 1955:Length 1587:NO_LLGR 1397:Lowest 1256:1 = EGP 1254:0 = IGP 1231:AS-path 1137:Default 1063:Loc-RIB 1059:Loc-RIB 1051:Loc-RIB 1014:Loc-RIB 943:Please 698:peering 634:routers 561:History 520:routing 468:more... 452:Tunnels 428:more... 361:more... 311:more... 300:TLS/SSL 255:ONC/RPC 192: ( 127:tcp/179 123:Port(s) 90: ( 70:Purpose 4330:15 Aug 4132:delay. 4061:"Info" 4040:"Info" 4019:"Info" 4001: 3858: 3750: 3578: 3239:Quagga 3120: 2931:, and 2809:, and 2722:, and 2547: 2482:. The 2333:Cease 1978:octets 1974:Length 1968:Marker 1924:24–31 1921:16–23 1750: 1741:NOPEER 1730: 1710: 1690: 1658: 1622: 1511: 1491: 1471: 1452: 1342:oldest 1251:ORIGIN 1185:Higher 1163:Higher 1084:(MED). 678:border 577: 295:Telnet 194:HTTP/3 133:RFC(s) 4356:(PDF) 4349:(PDF) 4276:Cisco 4214:Cisco 4114:(PDF) 4092:(PDF) 4085:(PDF) 3978:Cisco 3712:Cisco 3491:(PDF) 3484:(PDF) 3373:Notes 3267:team. 2444:Rules 2131:Name 1958:Type 1918:0–15 1245:"IGP" 1202:"Off" 1160:"Off" 1146:NOTE 1131:Scope 422:IPsec 200:HTTPS 4843:4893 4836:3392 4829:3065 4822:2858 4815:2796 4808:1965 4801:1771 4794:1657 4787:1655 4780:1654 4773:1105 4754:9552 4747:8955 4740:8642 4733:8195 4726:8092 4719:7911 4712:7606 4705:7153 4698:6793 4691:5701 4684:5492 4677:5065 4670:4760 4663:4724 4656:4456 4649:4360 4642:4278 4635:4277 4628:4276 4621:4275 4614:4274 4607:4273 4600:4272 4593:4271 4586:3765 4579:2918 4572:2439 4565:1997 4558:1772 4474:4893 4457:IETF 4332:2014 4004:4456 3980:.com 3955:4271 3860:4360 3843:2015 3752:1997 3735:.com 3714:.com 3693:2547 3659:2858 3625:2842 3581:4271 3532:2021 3499:2018 3437:2023 3429:IETF 3342:QPPB 3296:Ixia 3287:GNS3 3271:XORP 3259:, a 3221:, a 3219:BIRD 3205:view 3147:Uses 3129:MPLS 3122:4760 3001:and 2959:and 2884:ICMP 2641:TCAM 2635:and 2629:eBay 2549:2439 2422:OSPF 2374:7313 2128:Code 2120:Name 1984:Type 1952:128 1752:3765 1732:1997 1712:1997 1692:1997 1660:7999 1624:9026 1513:7611 1493:8326 1473:1997 1454:1997 1394:"on" 1376:"on" 1358:"on" 1339:"on" 1297:"on" 1208:AIGP 1134:Name 1128:Step 1090:(AS) 670:eBGP 658:iBGP 642:port 618:IPv4 614:4271 598:4271 594:1771 590:1654 583:2283 579:1654 571:IPv6 555:EBGP 547:iBGP 417:IGMP 397:ICMP 355:QUIC 350:RSVP 345:SCTP 340:DCCP 305:XMPP 285:SNMP 280:SMTP 265:RTSP 240:OSPF 230:NNTP 225:MQTT 220:MGCP 215:LDAP 205:IMAP 190:HTTP 170:DHCP 4471:RFC 4461:doi 3999:RFC 3952:RFC 3942:doi 3856:RFC 3748:RFC 3690:RFC 3680:doi 3656:RFC 3646:doi 3622:RFC 3612:doi 3576:RFC 3223:GPL 3118:RFC 3015:). 2973:to 2621:Y2K 2545:RFC 1947:96 1942:64 1937:32 1834:IXP 1748:RFC 1728:RFC 1708:RFC 1688:RFC 1656:RFC 1620:RFC 1509:RFC 1489:RFC 1469:RFC 1450:RFC 1008:RIB 947:to 702:VPN 680:or 672:or 660:or 638:TCP 575:RFC 557:). 512:BGP 462:MAC 457:PPP 447:ARP 412:ECN 407:NDP 335:UDP 330:TCP 290:SSH 275:SIP 270:RIP 260:RTP 250:PTP 245:POP 235:NTP 210:IRC 185:FTP 180:DNS 165:BGP 104:EGP 65:BGP 4877:: 4537:, 4533:, 4491:. 4469:. 4459:. 4455:. 4416:. 4398:. 4380:. 4323:. 4293:. 4274:. 4256:. 4245:^ 4231:. 4212:. 4187:. 4148:. 4129:. 4116:. 3997:. 3975:. 3950:. 3874:. 3814:. 3790:. 3766:. 3730:. 3709:. 3688:. 3678:. 3654:. 3644:. 3620:. 3610:. 3574:. 3552:. 3534:. 3522:. 3516:. 3486:. 3453:. 3427:. 3042:18 3028:18 3011:18 2997:17 2983:17 2969:18 2955:18 2941:18 2927:18 2917:, 2913:18 2899:16 2878:16 2864:18 2851:. 2847:16 2833:16 2819:18 2805:18 2795:, 2791:18 2781:, 2777:16 2760:18 2746:18 2732:18 2718:18 2708:, 2704:18 2690:16 2669:24 2631:, 2619:A 2559:. 2376:. 2356:. 2306:11 2298:10 1929:0 1878:10 1874:# 1849:# 1388:12 1370:11 1352:10 1123:: 1045:, 1003:: 907:: 890:: 869:: 832:: 798:: 757:: 538:. 401:v6 390:v6 385:v4 380:IP 174:v6 4862:) 4515:. 4501:. 4476:. 4463:: 4439:) 4420:. 4402:. 4384:. 4365:. 4334:. 4308:. 4260:. 4216:. 4198:. 4173:. 4070:. 4049:. 4028:. 4007:. 3982:. 3957:. 3944:: 3923:. 3884:. 3845:. 3824:. 3800:. 3776:. 3737:. 3716:. 3695:. 3682:: 3661:. 3648:: 3627:. 3614:: 3584:. 3501:. 3468:. 3439:. 3039:/ 3025:/ 3008:/ 2994:/ 2980:/ 2966:/ 2952:/ 2938:/ 2924:/ 2910:/ 2896:/ 2875:/ 2861:/ 2844:/ 2830:/ 2816:/ 2802:/ 2788:/ 2774:/ 2757:/ 2743:/ 2729:/ 2715:/ 2701:/ 2687:/ 2666:/ 2543:( 2330:6 2322:5 2314:4 2290:9 2282:8 2274:7 2266:6 2258:5 2250:4 2242:3 2234:2 2226:1 2220:3 2212:6 2204:5 2196:4 2188:3 2180:2 2172:1 2166:2 2158:3 2150:2 2142:1 2136:1 1333:9 1309:8 1288:7 1263:6 1239:5 1216:4 1196:3 1173:2 1151:1 970:) 964:( 959:) 955:( 941:. 668:( 656:( 553:( 545:( 510:( 496:e 489:t 482:v 403:) 399:( 196:) 176:) 172:( 94:) 34:. 20:)

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