I have a bm 3.8 box with 3 NICS and have a funny problem.

I have a public nic, private nic and dmz nic.
The address of the private nic is 10.1.1.34
The address of the dmz nic is 10.10.1.34
Tunnel address is 10.99.0.0
pool address is 192.168.251.1-50

The weird thing is
if a vpn client on the internet pings a device on the private network the device on the private network gets the request from 10.1.1.34.
if a vpn client on the internet pings a device on the dmz network the device on the dmz gets the request from 192.168.251.x and only gets the reply if I put a route on the dmz device for the 192.168.251 network.

So yes my installation works but I would like to know why the above is happening. I'd of thought that if the private network is receiving the vpn client requests from 10.1.1.34 then surely the dmz devices should be receiving vpn client requests from 10.10.1.34

Any ideas
Thanks
Gary