Route Policies - Avaya 8800 Configuration Manual

Routing fundamentals
On an Ethernet Routing Switch 8800/8600, default preferences are assigned to all standard
routing protocols. You can modify the default preference for a protocol to give it higher or lower
priority than other protocols. When you change the preference for a route, if all best routes
remain best routes, only the local route tables change. However, if a change in the protocol
preference causes best routes to no longer be best routes, neighboring route tables can be
affected.
In addition, you can modify the preference value for dynamic routes through route filters or IP
policies, and this value overrides the global preference for the protocol. You can use alternative
mechanisms to change the behavior of specific routes to have a different preference rather
than by acquiring the global protocol preference. For a static route, you can specify an
individual route preference that overrides the global static route preference. The preference
value can be any number from 0 to 255, with 0 reserved for local routes. 255 represents an
unreachable route.

Route policies

When the Ethernet Routing Switch 8800/8600 routes IP traffic, a number of route policies
(filters) can be applied to manage, accept, redistribute, and announce policies for unicast
routing table information. The filtering process relies on the IP prefix lists in the common routing
table manager infrastructure. Filters apply in different ways to various unicast routing
protocols.
The following figure shows how filters are applied to the BGP, RIP, and OSPF protocols.
Figure 6: Route filtering for unicast routing protocols
22 Configuration — OSPF and RIP June 2011