Avaya Configuring IP Exterior Gateway Protocols (BGP and EGP) Instrukcja Użytkownika Pobierz pdf (Strona 117)

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7-1

Chapter 7

Configuring BGP Accept and Announce Policies

BGP accept and announce policies govern which routes a router uses and which

routes it propagates to other routers. Appendix B, “Routing Policies

” describes

the BGP accept and announce policy parameters.

So that every BGP border router within an AS comes to the same decision in

constructing path attributes for an external path, routing policies must be

coordinated among all BGP speakers within an AS. Nortel Networks

recommends that the accept and announce policies on all IBGP connections

accept and propagate all routes. On external BGP connections, you must make

consistent routing policy decisions.

When a BGP speaker receives a route in an update message, it applies any local

routing policies to determine whether the router will use the route and whether it

will propagate the route to other routers. Then, if the route can be used, it is

compared against routes from other protocols and possibly included in the

forwarding table.

Note:

By default, an external BGP-3 or BGP-4 speaker will neither advertise

any routes to a peer, nor inject any routes into its IGP. Route policies must be

configured to enable any route advertisement.

Note:

In addition to announce and accept policies, Nortel Networks supports

import and export filters for BGP-3. Import and export filters provide a subset

of the parameters provided by the policies. For information about configuring

import and export filters, see Configuring IP, ARP, RARP, RIP, and OSPF

Services.

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Avaya Configuring IP Exterior Gateway Protocols (BGP and EGP) Instrukcja Użytkownika Strona 117