Hi - apologies for this rather longwinded question but I've melted my head trying to do this!!!
I have an unusual routing problem I could do with some help on. We've got an Xserve that has an internal IP address of 192.168.1.10/24 on en0 using 192.168.1.249 as it's router, with the router's NAT table on a one-one from 1 of 5 external IP addresses (I'm going to call this Connection1 for ease of speech!). Fine, it works a treat.
We also want to provide a secondary way into that server via another broadband connection (different external IP addresses) into en1. I currently have en1 set up as 10.1.0.2/24 using a second router set up as 10.1.0.1. These 2 devices are discretely connected via CAT5.( This is Connection2.)
This is where my problem lies. As long as en0 remains the primary interface, any connection I try to make from the outside world via Connection2, simply times out. Using tcpdump on the connecting machine shows that the responses are coming back from Connection1 not Connection2, so no wonder.
But this is where I'm confused. I thought that an originating packet from 10.1.0.1 (incoming via the external IP address) would be sent back to it? I didn't expect it to just send it back out via the default gateway? How can I get the Xserve to send packets back via the interface they came from and not anywhere it likes? I've tried using route to manually add in entry into the routing table but it won't take it as one for 10.1.0/24 already exists!!
NAT is not on and the Firewall isn't a factor either (it does it whether the Firewall is on or not)
Anybody still reading this, you have my deepest gratitude and you'll get my eternal love (easy tiger!) if you can solve my puzzle.
Cheers