Slow Nortel Contivity VPN downloads

We have some employees that access remote networks using Nortel Contivity VPN client. During the course of their duties they download large files and have issues with painfully slow (1-2 kb/s) download speeds in the application they are using. After much head banging and support technician stumping we finally found the cause.

Our firewall is a cisco based product and for some reason the Nortel Contivity VPN client did not like using the dynamic NAT address pool we had set aside for use by outbound connections. To resolve the issue we had to configure each computer that used the Nortel Contivity VPN client with a static NAT entry in the firewall. That caused their download speeds to jump from 2 kb/s to over 150 kb/s.

Just as a note, there were no errors reported in the firewall logs and no errors found by the Cisco engineers in the packet traces. Everything appeared to be fine. They are doing a little research to see if they can tell me why this was happening.

I'll let you know what I find out.