A Border Gateway Protocol 4 (BGP-4), March Canonical URL: https://www. ; File formats: Plain Text PDF; Status: DRAFT. Connected: An Internet Encyclopedia RFC RFC Network Working Group Request for Comments: A Border Gateway Protocol 4 (BGP-4). RFC A Border Gateway Protocol 4 (BGP-4) (Q). request for comments publication. RFC; A Border Gateway Protocol 4.

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Archived from the original on Retrieved March 16, The major enhancement was the support for Classless Inter-Domain Routing and use of route aggregation to decrease the size of routing tables. In addition, and perhaps even more importantly, larger routing tables bbp longer to stabilize see above after a major connectivity change, leaving network service unreliable, or even unavailable, in the interim.

If one router implementation takes more memory per route than another implementation, this may be a legitimate design choice, trading processing speed against rgc. This mechanism consists of a set of rules. A single router or two for redundancy can be made a route reflector: Nevertheless, these are common tools for experienced BGP network architects.

Once candidate routes are received from neighbors, the Loc-RIB software applies additional tie-breakers to routes to the same destination. At the second occurrence, BGP shuns that prefix for a certain length of time; subsequent occurrences are timed out exponentially.

Please consider expanding the lead to provide an accessible overview of all important aspects of the article. The main difference between iBGP and eBGP peering is in the way routes that were received from one peer are propagated to other peers. Examples of common communities include local preference adjustments, geographic or peer type restrictions, DoS avoidance black holingand AS prepending options.

The BGP design is such that delivery of traffic may not function while routes are being updated. Theory and Applications” PDF. Route reflectors and confederations both reduce the number of iBGP peers to each router bgpp thus reduce processing overhead.


Not all ISPs give out their communities to the public, while some other do. From Wikipedia, the free encyclopedia. Depending on the implementation of that process, the BGP route is not necessarily selected. A BGP speaker sends byte keep-alive messages every 60 seconds [5] to maintain the connection. This page was last edited on 5 Decemberat Route reflectors are a pure performance-enhancing technique, while confederations also can be used to implement more fine-grained policy.

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.

RFC A Border Gateway Protocol 4 (BGP-4) – Wikidata

Please integrate the section’s contents into the article as a whole, or rewrite the material. The neighbor could send several possible routes to a destination, but the first level of preference is at the neighbor level. The first decision point for evaluating NLRI is that its next-hop attribute must be reachable or resolvable. BGP4 has been in use on the Internet since 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.

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 bpg. In the simplest arrangement, all routers within a single AS and participating in BGP routing must be configured in a full mesh: If AS1 later decides to drop the route In the network as a whole it is normal for these changes to happen almost continuously, but for any particular router or link, changes are supposed to bg relatively infrequent.

This article’s lead section does not adequately summarize key points of its contents. RFC corrected errors, clarified ambiguities and updated the specification with common industry practices.


Their structure is not visible to other BGP routers, although they usually can be interrogated with management commands on the local router.

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. Confederations can be used in conjunction with route reflectors. Inonly AS numbers were still available, and projections [30] were envisioning a complete depletion of available AS numbers in September AS2 will see the three routes, and depending on the routing policy of AS2, it will store a copy of the three routes, or aggregate the prefix’s A feature known as route flap damping RFC is built into many BGP implementations in an attempt to mitigate the effects of route flapping.

How routes are propagated can be controlled in detail via the route-maps mechanism.

Border Gateway Protocol

Other deployment topologies are also possible, such as running eBGP peering inside a VPN tunnel, allowing two remote sites to exchange routing information in a secure and isolated manner. By using this site, you agree to the Terms of Use and Privacy Policy. To alleviate the problem, BGP implements two options: For a multi-homed network, if it announces the same network blocks across all of its BGP peers, the result may be that 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 bbp as optimal.

Such cases rf increase the number of routes as seen on the global BGP table.

Products marketed as switches may or may not have a size limitation on BGP tables, such as 20, routes, far smaller than a full Ngp table plus internal routes.

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