Nortel Networks NN47200-503 Accept In Policies, Announce Out Policies, Redistribution Policies

36An Introduction to IP Routing Protocols

Route policies supports the following types of policies:

•Accept (In) Policies

Accept polices are applied to incoming routing updates before they are applied to the routing table. In the case of RIP, accept policies can be applied to all incoming packets and only one policy can be created for each RIP interface. In the case of OSPF, accept policies are only applied to Type 5 External routes based on the advertising router ID. There can only be one OSPF accept policy per switch and the policy is applied before updates are added to the routing table from the link state database.

•Announce (Out) Policies

Announce policies are applied to outgoing routing updates before the routing update packets are actually transmitted from the switch. In the case of RIP, announce policies can be applied to all outgoing packets and only one policy can be created for each RIP interface. Announce policies are not supported for OSPF as OSPF requires routing information to be consistent throughout the OSPF domain.

•Redistribution Policies

Redistribution policies are used to provide notification of addition or deletion of a route in the routing table by one protocol to another protocol. OSPF redistribution policies send redistributed routes as Type 5 External routes. There can be only one OSPF redistribution route per switch and it must be configured as a ASBR with redistribution enabled.

Route policies consist of the following items:

•Prefix Lists

—List of IP addresses with subnet masks.

—Identified by a prefix list name and unique identifier.

—Prefix lists support the comparison of ranges of incoming masks.

•Route Maps

—Contain a set of match and set parameters.

—Match and set parameters can contain several prefix lists.

—A set of match and set parameters are identified by a sequence number.

—Accept and deny actions are associated with each sequenced parameter set.

—Sequence numbers act as a preference setting. Sets with a lower sequence number are preferred over those with a higher sequence number.

Nortel Ethernet Routing Switch 5500 Series

Configuration-IP Routing Protocols

NN47200-503 03.01 Standard

5.127 August 2007

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