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Bronze

CEF and route caching

Hi,

I want to know why CEF is less CPU-intensive than fast switching route caching?

is that using another hardware like ASICs or has optimizing algorithm?

I would be appreciate if you advice me.

Kind Regards,

M.A.Rad

2 REPLIES
VIP Purple

Re: CEF and route caching

Hello,

CEF uses a Forwarding Information Base, which is an identical copy of the routing table. In dynamic networks, fast-switched cache entries are frequently invalidated due to routing changes. These changes can cause traffic to be process switched using the routing table, rather than fast switched using the route cache. The subsequent lookups in the routing table cause higher CPU utilization.

Because the Forwarding Information Base (FIB) lookup table contains all known routes that exist in the routing table, it eliminates route cache maintenance and the fast-switch or process-switch forwarding scenario. CEF can switch traffic more efficiently than typical demand caching schemes.

HTH,

Georg

Gold

Re: CEF and route caching

CEF also uses an optimized lookup table, primarily enabled by its use of the adjacency and loadinfo tables rather than just storing all the information (including the mac header rewrite) in the table. In technical terms, CEF uses a trie, rather than a tree. There are other differences as well, but the ones Georg has pointed out, and the differences in the data structure, are the main ones.

:-)

Russ.W

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