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New Member

VPN Performance on 2621 Routers


we've got a vpn-tunnel established between two 2621 Routers and have the AIM/BP Encryption Card installed. It work's, but the Performance is not quite what we expected. We've got Windows 2000 and Windows NT Servers on one tunnel-end, and the Performance of the NT Server is only about 1/3 of the Windows 2000.

Has anyone got any hints about tuning my VPN ?

Would it make a difference changing from §DES to DES ?

What is the best tcp/ip packet size for my tunnel ?

thanks, steve

New Member

Re: VPN Performance on 2621 Routers

So you’re getting better performance across the VPN with Windows 2000 vs. NT? This may have nothing to do with the VPN. Have you timed large ping packets across the tunnel from both machines to compare? I know there will be some performance loss with 3DES over DES but 3DES is far more secure. 3DES performance with hardware acceleration, 1400 byte packets is rated at about 6 Mpbs according to this grid

New Member

Re: VPN Performance on 2621 Routers

Hi Steve,

I have the same issue here,

we have 2 2621 terminating the VPN and we have a bad performance on our vpn

when we do a traceroute within the vpn we have something like 2000ms delay in the respnse and when we do the same across the provider network, the delay is quite normal (20ms)

Did you find how to improve your vpn perfirmance?

For the packet size, I don't know, but it could impact the performance if your size is too small.

As your message is quite old, maybe you have already a solution for that issue.

thanks a lot for your help



New Member

Re: VPN Performance on 2621 Routers


we still haven't solved our problem with the perfomance. Cisco told us to turn off "fast-switching-mode" on the LAN Side of the tunnel, but this cut our performance overall by 50%. According to Cisco the VPN encyption card should be doing 6MBit, how much performance do you get (we get about 300-400KByte on av., compared to the theoretical 768KByte).