How to Ensure That Packets Are Switched at Speed Fast

To fast-switch policy-routed traffic, ensure the following:

• Fast switching of policy routing is disabled by default. It must be manually configured.

• Configure policy routing before you configure fast-switched policy routing.

• When policy routing is configured, turn on the fast switching with this interface command:

ip route-cache policy

• Fast-switched policy routing supports all of the match commands and most of the set commands, except for the following restrictions:

— The set ip default command is not supported.

— The set interface command is supported only over point-to-point links, unless a route-cache entry exists using the same interface specified in the set interface command in the route map. In addition, when process switching, the routing table is consulted to determine a path to the destination. During fast switching, the software does not make this check because fast switching is a cache of the process switch lookup. Instead, if the packet matches, the software blindly forwards the packet to the specified interface. This is a similar situation to the one described in reference to load balancing earlier.

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