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Module ISM-VPN-29 for C2911

Hello everybody.

Can't find out about one thing.

On I have read the next about ISM-VPN-29 module for my C2911

"The Cisco 2900 Series Module (ISM-VPN-29) can  provide hardware-based IPSec encryption services of 145 and 550 Mbps in  the Cisco 2901, 150 and 600 Mbps in the Cisco 2911, 220 and 700 Mbps in  the Cisco 2921, and 385 and 900 Mbps in the Cisco 2951 (IPSec IMIX and  1400-byte packets)."

There are two speeds "150 and 600 Mbps in the Cisco 2911".

For what? And why the differance is so big?

Please explain me.

VIP Purple

Re: Module ISM-VPN-29 for C2911

You are already quoting the difference: (IPSec IMIX and  1400-byte packets).
It's for different traffic. Nearly every networking device can achieve a higher throughput with bigger packets. That are the 600 MBit/s which are measured with packets of 1400 bytes. But with IMIX-traffic the router has to process many more small packets which slows him down. But it's much nearer to the throughput you'll get in reality than the value measured with big packets.

More on IMIX:

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Related question - are the

Related question - are the numbers one-way or aggregate for both directions?


I think it's the latter, because the 2921 maxes out at around 500 Mbps for one-way using unencrypted traffic and that's with large packet size. 

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