routing between 2 networks with same IP

[yoda291]

ok, I have a small situation. I'm trying to bridge between two networks where clients have the same subnets and some even have identical IP addresses. Everything is done statically in sync with the dns tables so changing IP isn't an option. I know how to forward packets and route like a normal person, but I imagine there'd be some pretty big conflicts routing from network A to network B. I imagine it's a simple thing as it seems like a common enough problem, I'm just clueless. I'm using win2k Advanced server to route packets between the two networks(2 NICS).

 

[ScottMac]

You can't do it without a lot of grief, if at all...especially with some stations on the same addresses.

The hangup would be to get the local devices to send (what they think are local) packets to the default gateway....there's just no mechanism to do that on the host side. NAT won't help, because you have no way to tell a host to send "local" packets to the default gateway to be NAT'd.

If you try to bridge the two, you'd get duplicate IP address errors. Tunneling won't work for the same reason. I don't THINK that you can create the right kind of rules for a policy route (send my address as both source and destination??? Not likely as far as I can figure...)

Probably your only chance there is to use an additional (as-of-yet) unused protocol (like maybe IPX) to create another protocol-network (with different network numbers), and do the LAN-LAN communication over the non-IP protocol. Use IP for each LAN-to-Internet connection on both sides. If the stations on the two LANs can use NETBIOS, then do the NETBIOS-over-IPX thing, and just route IPX between the LANS (then use seperate routers for LAN-to-Internet). You'd need seperate routers to different ISPs on each LAN side, and NAT them so the ISP has discreet addresses to differentiate the two.

That's as good as I can figure, maybe someone else has something.


Good Luck

Scott

 

[PlatinumGold]

if ur using w2k server anyway, i'd go for active directory w/ dhcp and ddns.

it might be a lotta trouble changing from static to dynamic ips, but in the long run, i think it'll be worth its. specially if combing the 2 networks is gonna be a permanent thing.

 

[spidey07]

You can run NAT between the two networks. Really depends on exactly how the DNS is set up. Pretty messy though...

http://www.cisco.com/warp/public/556/3.html