Is it possible replace a 3745 router by a 2811

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Mar 6th, 2008
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The 3745 router is reaching 95% cpu usage, the customer has a 2811 that is smaller, but is newer, the memory of both devices are the same. Does someone know if the 2811 will be better than the 3745?

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pnicolette Thu, 03/06/2008 - 17:47
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Cisco rates the 2811 for max of 3K pkts/sec process-switched and 120K fast-switched. (These are 64-byte packets with no processing.)

3745 doesn't list a process-switched rate but says 225-250K fast-switched.

Assuming nothing in the config forces unneeded process switching (worth checking?), maybe it's time for a 3845 (500K fast-switched).

Joseph W. Doherty Thu, 03/06/2008 - 18:13
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95% spikes, or a long term average? Interrupt % or total CPU?

The 2811 pps is about half that of a 3745, so likely not advisable.

Depending on actual CPU usage % and type of usage, and if doing just WAN routing, agree with Paul, you probably should consider a 3845 or larger.


If the router is just doing LAN routing, a better option would be to use a multilayer switch, e.g. 3650/3750. If the router is doing both LAN and WAN routing, and it's the LAN routing that generating the most traffic, front it with a multilayer switch to off-load the LAN portion. (Perhaps a 3560-8PC)


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