TomatoUSB

I frequently use Cisco VPN to VPN to my work network. I've just discovered that with QoS enabled, the VPN tunnel does not work at all. Why would this be and does anyone know how to fix it? I've had to turn off QoS to be able to work and QoS was a feature I really liked.

More details…

Router = WL-520GU
Tomato Firmware v1.28.8750 ND USB vpn3.6

Example process:
1. Computer connected to internet with no issues and Tomato QoS on
2. Make Cisco VPN connection
3. Connection established (according to the VPN client software)
4. Absolutely no internet connection after this… can't ping direct google IPs
5. I tried putting my pc in a DMZ and it made zero difference
6. Disconnect everything and turn QoS off
7. VPN then works great

Thanks,
Russ

All I can tell you is that I'm using QoS, and connect to several different VPNs using Cisco VPN client with no problems.

For further troubleshooting, refer to this post.

I had a similar problem and it was because I was using the default Toastman settings which cause the Cisco VPN traffic to fall into the lowest (Class E) which had an outbound limit of 1%. I fixed it by adding a classification for UDP Dest Port 500, 4500, 10000 and moving it to a higher class and also moving this rule above the UDP Dest Port 1-65535 rule which was previously putting my VPN traffic within Class E. I had tried an L2TP rule as someone else had specified but it didn't work for me. The ports I ended up using I found in another post, technically I've only seen 4500 in use though.

By the way I found the "QOS - View Graphs" page to be very useful in troubleshooting QOS problems. Clicking on a classification will show the connections falling into that classification. If there aren't too many connections when you're troubleshooting it's easy to see what connections are matching lower than expected rules as well as the details to alter your classifications to fix it.

I think he has the same problem as me. If I use the Quick QoS Script, it kills the VPN (there are a ton of errors in the log).
The WL-520GU doesn't seem to have much RAM, it may be the problem (like my WRT54GL).
I resolved it by entering the rules one by one and removed some of them.