VPN Passthrough problems with Airport Extreme Today I started trying to work from a network that uses the Airport Extreme version 7.7.1.  Typically I use a VPN client (Viscosity) which gives me access to the various servers that my company runs on.  I can connect to the open VPN without any issue but am experiencing mixed results from there forward.  

Once connected to the VPN I can access a couple of the servers through a web browser and SSH from the command line but timeout while trying to connect to the rest.  If I bypass the router and plug directly into the modem via ethernet everything works perfectly.

I've tried setting up port forwarding on the Airport Extreme with no success and disabling "Back to My Mac" settings.  There are a number a threads out there where people have had issues with VPN and the Airport Extreme but nothing quite like this.

I'm baffled why I can connect to the VPN and some of the servers while others are failing.   Again, I am sure that the VPN/servers are configured properly as this problem goes away when I remove the router from the picture.

Please let me know where I'm going wrong!
The problem was that the Airport Extreme router was configured to use the same range of IP addresses as the VPN, so while I was able to connect to the VPN there was some issues when trying to SSH into some of the servers where there was an IP conflict.  It is possible to change the "IPv4 DHCP Range" in the advanced network options of the Airport Extreme which solved my issue.