Connecting Separate LAN’s Through Routers

connecting networks
I have two LAN's in my office, each with its own internet connection. I'll call them LAN A and LAN B. Each LAN has an inexpensive ADSL modem router (with wireless and wired connections) to which the computers attach and which attach to the internet. I want to share information and printers etc. between the two LAN's and on occasion I may want to be able to access (from one LAN) the other LAN's internet connection. I want to be able to "see" the computers on each of the LAN's from the other LAN. LAN A uses the addresses 10.0.0.x, and the router itself has the address LAN B uses the addresses 192.168.11.x and the router itself has the address The routers are from different manufacturers. I understand that I have to set up routing tables on each of the routers, and I want to connect them (with cable). I believe that on LAN B router I set up a routing entry as follows: Dest: Netmask: Gateway: some IP address? On LAN A router table, I would do this: Dest: Netmask Gateway: some IP address? My questions are: Is my understanding above correct? How should the two routers be physically connected and addresses set up? I can plug an RJ45 cable between the LAN A and LAN B router (both on the in-facing side), but as both routers are setup as DHCP servers for the computers on their respective LAN's I do not understand how each router will assign the other router with a relevant IP address - in effect they are only DHCP clients on the WAN side. I have tried wiring them up like this and they do not seem to assign IP addresses correctly. Ideally, I think I want to tell each router to have a particular address (an IP or a hardware address) in respect of the other router, but I cannot see how to do this. On one of the routers I can give the DHCP server the MAC address of the other router and define an IP address for it, but the other does not seem to have a similar facility to reciprocate. They both have user definable routing tables so there must be some way of doing this, and maybe I am looking in the wrong place or simply I do not have the concept correct? i would be grateful for any feedback on that. Is there any merit in using domains to facilitate finding resources on the other LAN, if I ever get the routing correct? Many thanks.

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What you need is a router that has two FastEthernet interfaces that can be assigned IP addresses. The Cisco 2811 has two FE interfaces but may be overkill…I’m not familiar with any smaller models.

On interface FE1 assign it an IP address of and connect it to LAN A modem. The login to LAN A modem and define a route 192.168.11.x to gateway

On interface FE2 assign it an IP address of and connect it to LAN B modem. Then login to LAN B modem and define a route 10.0.0.x to gateway

This will enable both networks to “see” each other. As for sharing files and printers, you would probably need to setup a domain, like Microsoft Active Directory.

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  • Thegoodpoet
    Tbitner is on the right track and that would work. However it sounds like this offic is already on a domain since it has an IP address beginning with 10.x.x.x. Sounds like all you may need is a a router with one ethernet port. you can subdivide the one ethernet port by assigning VLANs (Router on a stick)
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