I have a border router doing NAT using the overload keyword. Using this configuration on 12.1.27b, I was able to connect to a remote vpn connection from a computer on the internal network to a remote network (nat inside/outside). This worked for the IPSec tunnel but didn't allow for any traffic through the tunnel. The configuration was as follows:
ip nat inside source list IP_NAT_LIST interface FastEthernet0/1 overload
ip access-list standard IP_NAT_LIST permit 10.10.0.0 0.0.255.255
I then upgraded to 12.3.16a and added the following line to the configuration:
ip nat service fullrange udp port 500 ip nat inside source list IP_NAT_LIST interface FastEthernet0/1 overload
ip access-list standard IP_NAT_LIST permit 10.10.0.0 0.0.255.255
Now all traffic is being sent over the tunnel. I think I understand what happened here but I wonder if someone with more expertise would enlighten me, many thanks in advance.