VPN Client problems on router. Works fine on BB modem

[charlesr]

Anyone know stuff about VPNs? I'm trying to fix this for someone. When using BT BB Modem, he could quite happily connect with a VPN to the gateway at his shop and check the shop systems. Now he's got a 3com wireless router and although the VPN connects, when he tries to run the shop accounts software, it comes up with a useless generic error message about not being able to connect.

It's the Sonic Wall Global VPN Client and on the knowledge base on their website, it says:

The following services need to be opened on any router or firewall in the VPN path:
UDP port 500 for IKE
IP protocol 50 for IPSec

I've opened port 500 for udp, but what's that other thing? Is that port 50 needing to be opened too? I tried that anyway and it didn't work. Any suggestions anyone?

The router is 3com 3crwdr100a-72

Thanks

[charlesr]

I'm now hoping it was just the ip of the router conflicting with the ip of the vpn gateway. I've changed the router ip to 192.168.1.2 but now have to wait until the gateway comes back on after the nightly backup. Would still like to know what that ipsec 50 stuff is about if anyone knows though please.