I have two different routers connected to different ISPs having different LANs. I want to set up the network in such a way that we can connect to devices on the other LAN or ping devices on the other network. One router has DHCP enabled. NAT is enabled on both of the routers.

I have tried putting in a static router but I am not sure if I am doing it right. I want to connect to computers, DVR and other devices. Right now I change 0 and 1 in the IPs to switch between networks. Is there a way to do it?

Router A's settings: IP Address: Subnet Mask:

Router B: IP Address: Subnet Mask:

(                      (
WAN 1> Router A> Switch1-----------Switch2< Router B(DHCP) < Wan 2
         |                                      |
Computers and Printer              Computers, IP Phones and DVR

You can plug a router in between Switch A and Switch B (from here on referred to as Router C, with ip addresses 192.168.0/1.254), and set up two static routes on the gateway routers to route between the two networks.

On Router A: A route to with subnet mask using the 192.168.1.x address of Router C

Example (Cisco IOS command): ip route

On Router B: A route to with subnet mask using the 192.168.0.x address of Router C

Example (Cisco IOS command): ip route

It is absolutely not necessary that this Router C be a Cisco device, I've simply included the Cisco syntax as it is what I am familiar with to be used as an example.

There may be a way to do this using just a cable connected between Router A and Router B if they have spare ports on them, but that would largely boil down to specifics about the capabilities of the routers you are using, while the above example should work on just about any equipment (I personally just ran a simulation in Cisco's Packet Tracer to make sure it was accurate).

  • If you have a layer 3 switch in your network at all, you can avoid needing a new router by just plugging the two routers into it and configuring separate vlans, along with vlan interfaces, for the separate LAN's. Use the same method as given above to set the routing tables up on router A and B. This is less likely to be the best solution for you, hence it being in a comment, but is thrown in for completeness. – 0xDAFACADE Aug 13 '14 at 23:15
  • 1
    I used Cisco 851 to do this. Configured one ip on the WAN side and another on VLan1 cuz this router is a hybrid router and has Ethernet ports in switch mode. Plugged the router in the network and added static routes and it worked! Thanks for your help – Kunwar Aug 27 '14 at 0:35

Your issue is that you have two networks that are bespoke for the attached devices IE if computer 1 and 2 are attached to Network A, and computers 3 and 4 are attached to Network B, they cannot interconnect

What you would need to do is connect all 4 PC to network A, and then via a separate network adapter also connect them to network B. You could, connect via wireless to one and via Ethernet to the other.

Then all computers can share other devices on both networks.

  • 1
    this doesn't really answer anything... – cp2141 Aug 13 '14 at 23:02
  • 1
    This method will work, but assumes you can install extra nic's into your various network equipment such as the DVR mentioned in the question. It also poses scaling issues that leave it as a less than ideal solution once you get beyond a handful of devices, making a router (or layer three switch between the two routers) a more elegant solution. – 0xDAFACADE Aug 13 '14 at 23:05

I tried a different approach using the same cisco 850 series router. I configure ip of router A on the WAN side of the router and IP of the router B on LAN side of the router. Ie

Router A( ---- to WAN of cisco 850 then

Router B( ---- to one of the LAN port

then adding router form router 1 to next hop and from router b to next hop

and then I was able to ping from one network to another.


Personally I'd get a 3rd router or switch. Set that up as your default ap subnet and let it handle nat and dhcp for the other two.DMZ on whichever of the two services has the quickest connection of twoandngomfrom there.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.