
Configuring IP Services
6-22 114065 Rev. A
Configuring Routing 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 between all of the BGP speakers within an AS. It is suggested that the
accept and announce policies on all IBGP connections accept and propagate all
routes. On external BGP connections, consistent routing policy decisions should
be made.
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.
You set values in BGP-4 accept and announce policy parameters to match and, in
some cases, override the attribute values contained in inbound and outbound
update messages.
Site Manager: Weight Value 1 parameter: page A-12
Site Manager: Weight Value 8 parameter: page A-14
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. In a future release, support for
import and export filters will be discontinued.
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