Cabletron Systems SmartSwitch manual Configuring Simple Routing Policies

Chapter 11: Routing Policy Configuration Guide

Many protocols allow the specification of two authentication keys per interface. Packets are always sent using the primary keys, but received packets are checked with both the primary and secondary keys before being discarded.

Authentication Keys and Key Management

An authentication key permits the generation and verification of the authentication field in protocol packets. In many situations, the same primary and secondary keys are used on several interfaces of a router. To make key management easier, the concept of a key-chainwas introduced. Each key-chain has an identifier and can contain up to two keys. One key is the primary key and other is the secondary key. Outgoing packets use the primary authentication key, but incoming packets may match either the primary or secondary authentication key. In Configure mode, instead of specifying the key for each interface (which can be up to 16 characters long), you can specify a key-chain identifier.

The SSR supports MD5 specification of OSPF RFC 2178 which uses the MD5 algorithm and an authentication key of up to 16 characters. Thus there are now three authentication schemes available per interface: none, simple and RFC 2178 OSPF MD5 authentication. It is possible to configure different authentication schemes on different interfaces.

RFC 2178 allows multiple MD5 keys per interface. Each key has two times associated with the key:

•A time period that the key will be generated

•A time period that the key will be accepted

The SSR only allows one MD5 key per interface. Also, there are no options provided to specify the time period during which the key would be generated and accepted; the specified MD5 key is always generated and accepted. Both these limitations would be removed in a future release.

Configuring Simple Routing Policies

Simple routing policies provide an efficient way for routing information to be exchanged between routing protocols. The redistribute command can be used to redistribute routes from one routing domain into another routing domain. Redistribution of routes between routing domains is based on route policies. A route policy is a set of conditions based on which routes are redistributed. While the redistribute command may fulfill the export policy requirement for most users, complex export policies may require the use of the commands listed under Export Policies.

The general syntax of the redistribute command is as follows:

ip-router policy redistribute from-proto <protocol> to-proto <protocol> [network <ipAddr- mask> [exactrefinesbetween <low-high>]] [metric <number>restrict] [source-as <number>] [target-as <number>]

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