
Configuring and Customizing BGP
303528-A Rev 00
8-55
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.
So that every BGP border router within an AS comes to the same decision in
constructing path attributes for an external path, route policies must be
coordinated among all of the BGP speakers within an AS. Bay 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.
This section covers the following topics:
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, Bay Networks supports
import and export filters for BGP-3. Import and export filters provide a subset
of the parameters provided by the policies.
Topic Page
Defining a BGP Accept Policy
8-56
Supplying Modification Values for a BGP Accept Policy 8-59
Specifying Matching Criteria for a BGP Accept Policy 8-61
Defining a BGP Announce Policy 8-63
Supplying Modification Values for a BGP Announce Policy 8-66
Specifying Matching Criteria for a BGP Announce Policy 8-70
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