Setting up OpenVPN on ubuntu / Mac os x troubleshooting

There are several reasons why you could be getting

GET INST BY VIRT: [failed]

One of the reasons is that your config for CCD doesn't include a route for a subnet sitting behind your client link 1

Also you will have to check that ip_forwarding is turned on in your sysctl

sysctl -p

and make sure that masquerading is enabled via iptables

iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE

These should sort out your problems