After a bunch of troubleshooting on a VPN access issue for a small business office, I eventually figured out what was causing the problem, but it doesn't seem to make any sense why it is a problem, and I'm hoping someone here who understands the technology better than I do can help me understand what's going on. The situation is basically this: I have computers on a home WiFi network using a current model Airport, and I'm trying to connect to a small office VPN to access a remote server. If I configure DNS servers manually on the computer's WiFi connection (that is, say, 220.127.116.11 for the DNS, if I use Google), and then connect to the VPN, everything works exactly as expected. If, however, I leave the WiFi DNS empty and let it get a DNS server from the Airport DHCP (in which case its DNS ends up being something like 10.0.0.1, while the Airport itself has 18.104.22.168 configured for the DNS), and connect the VPN, no VPN traffic goes anywhere. When connected to a VPN while using the Airport as a DNS relay (or cache, not sure which it does), even if I try to ping something directly via IP address--say, 192.168.111.1--no traffic gets through. If I route all traffic through the VPN, nothing goes anywhere--no internet at all. The local network is not on the same subnet as the remote network--the remote network uses 192.168.111.x while the local network is on 10.x.x.x (forget exactly what, but Apple's default) I'd sort of get it if the cached Airport DNS was causing some problems with routing to external addresses, but an IP address isn't supposed to hit the DNS at all, so I am completely baffled as to how the DNS setting on the WiFi connection is having any effect on the VPN'd connection. What am I misunderstanding here? What is OS X doing in terms of routing that's causing this?