Readvertised Route Policies; When To Use Route Policies - Alcatel-Lucent 7705 Configuration Manual

Configuring Route Policies

Readvertised Route Policies

Occasionally, within the network and as applicable to the VPRN service, BGP routes may be
readvertised from BGP into OSPF and IS-IS. OSPF export policies (policies control which
routes are exported to OSPF) are not handled by the main OSPF task but are handled by a
separate task or an RTM task that filters the routes before they are presented to the main OSPF
task.

When to Use Route Policies

The following are examples of when to configure and apply unique route policies:
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• when you want to control the protocol to allow all routes to be imported into the
routing table. This enables the routing table to learn about particular routes to enable
packet forwarding and redistributing of routes into other routing protocols.
• when you want to control the export of a protocol's learned active routes
• when you want the MP-BGP routing protocol to announce active routes learned from
another routing protocol (that is, the static routes configured in the 7705 SAR). This
function is sometimes called route redistribution.
• when you want unique behaviors to control route characteristics; for example, change
the route preference, AS path, or community values to manipulate or control the route
selection
• when you want to control BGP route flapping by use of route flap damping
7705 SAR OS Router Configuration Guide