We have many requests in the Network Forum on how to
properly add a second (or third) router to an existing LAN that already has a
The general setup of SOHO Router's is similar. While some use a different subnet, every one I've worked with uses a Class C Private IP Addressing Scheme. I'm going to use the basic Class C private for this tutorial (192.168.0.0)
I'm going to give two setup guides:
Version 1 will be for a simple, single
Version 2 will be cover separate subnets
The term “Router1” will refer to the router connected to the internet. Any others (ie: Router2, Router3) will be downstream of Router1
When connecting a second router to an existing LAN it’s easiest to connect LAN port to LAN port and configure the LAN side of the downstream router as compared to connecting to the WAN side.
Router1 (LAN Side):
DHCP Enabled = Yes
DHCP Scope: 192.168.0.100 to 192.168.0.199
Router2 (LAN Side):
Default Gateway: 192.168.0.1
DHCP Enabled = No
You will note in the above configuration that the LAN IP of Router2 is within the same subnet as Router1 but is outside of the DHCP Scope defined on Router1. This is important. If you use an IP within the scope, the DHCP service may attempt to give that IP to another computer you plug into your network. Using an IP outside of the scope avoids this potential problem. Also, devices like Routers, Servers, network printers should always have a statically assigned IP address so that the IP never changes.
If you have everything configured correctly, any computer plugged into Router2 will get an IP from the DHCP service on Router1 and will have full LAN and internet connectivity.
The DHCP Scope’s Default Gateway IP address should point at Router1 (192.168.0.1) as it is the gateway to the internet.
If you need to add another router, or two or three, simply
set the LAN IP on Router3 to 192.168.0.3 and configure all other TCP/IP
settings the same as Router2. Do the
same for any others you may add. I would
like to point out, using a switch makes more sense than using a router as a
switch requires no setup.
When you wish to have a separate, and secure, LAN attached to your
existing network you will need to segregate the new LAN using a
different, and separate subnet. In order to do this, and provide
internet connectivity to the new LAN, you will need to configure your
downstream router (Router2) and use routing to go between subnets. In
this case, you will use the WAN port on Router2 to connect to the
upstream router (Router1).