How do I combine two LANs?

October 4, 2005 6:25 PM

What do you do when two LANs fall in love and want to join together?

Some friends live in a house that's been split in half into a duplex type situation. Each side has their own internet connection and its own LAN. Now they want a LAN to connect the two sides of the house together. When they connect the two routers with a crossover cable router A takes it upon itself to assign the IP's for both LANs. How would we set it up so that doesn't happen, aside from assigning individual DNS ranges for each router? They both use Charter Cable, but don't want to combine services as they are both at the top speed and sharing bandwith is not an option.

posted by nadawi to Computers & Internet (2 answers total)

You ought to be able to do it using the routers by assigning different gateway addresses on the same subnet to the two routers (e.g. assign router A 192.168.0.1, assign router B 192.168.0.2) and manually configure all hosts to use an appropriate static IP address and gateway address so they talk to the right router. Then connect the two routers.

Alternatively, add an extra NIC to each machine and connect these to a switch (no router should be needed). The machines will assign a 169.x.x.x address on this port and should be able to see and communicate with each other this way.
posted by kindall at 6:42 PM on October 4, 2005

Yeah the second NIC would be easiest. But you should be able to do it using what you have. You'll have to make sure that both routers are set up as a different address, and you may have to manually set the gateway on each side to tell it to use that router. DHCP could be a problem, so I'd recommend disabling it and configure the IP address, netmask, and gateway manually in each machine. That way you don't have to worry about which router will answer the DHCP request when a machine asks for it. Just give each machine a unique address in rfc1918 space (normally 192.168.0.x).
posted by Rhomboid at 7:07 PM on October 4, 2005