It determines how the router switches packets.
If you use 'ip route-cache' then the router will be fast-switching the
packets. The router keeps a cached memory full of recently used (which
should often equal heavily used) routes & destinations. When a packet comes
in it can use that cache to determine where to send the packet without
having to do routing lookups.
If you use 'no ip route-cache' then the router will be process-switching and
will do route lookups for every packet.
I think Cisco recommends that if you are running a serial link that is
slower then T1 speed to go ahead and do 'no ip route-cache' because the link
is so slow (number of packets so low) that the time saved by the route-cache
isn't worth the memory of keeping all of that information.
Also, if you have multiple paths to the same destination and are doing
fast-switching, the router will load balance the traffic on a
per-destination basis because once the destination output port is in the
cache all traffic following it will go out the same port. Process-switching
will load balance on a per-packet basis since each packet is looked at
individually.
hope that helps,
Mike
>
>Can someone describe why I would want to use the ip route-cache (or no ip
>route-cache) command. I've found references on the Cisco site about how to
>use it, but not why.
>
>Tony Russell
>Network Engineer
>IBEAM Broadcasting
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