How to connect to an IPSec VPN through a LinkSys WRT54GL?

Question

I am having trouble connecting to a L2TP IPSec VPN when I use my wireless router. I have a LinkSys WRT54GL v1.1 wireless router with the most current version of tomato (1.28).

I have no issues connecting to the VPN server when I connect directly to the modem. I am using Windows 7 and its built-in VPN client.

Any ideas?

Answer 1

Enable the router's "VPN Passthrough" feature, which should be in the Advanced settings somewhere.

Of course, if you'd like to (or need to) get away from IPSec, I highly recommend OpenVPN which works without the need to enable the "VPN Passthrough" option:

  OpenVPN (free, open source, userland VPN solution)
  http://www.openvpn.net/index.php/open-source.html

Answer 2

No problem,

VPN passthrough just opens up your firewall with these options for IPSEC.

You need firewall rules to allow udp dest ports 500 & 1701. protocol gre/esp & ah in.

In iptables it would basically be this:

iptables -A FORWARD -p udp -m multiport --dports 500,1701 -j ACCEPT
iptables -A FORWARD -p gre -j ACCEPT
iptables -A FORWARD -p esp -j ACCEPT
iptables -A FORWARD -p ah -j ACCEPT

Of course that allows anyone to access your VPN potentially, so I'd recommend you filter that further by IP range if you can.