Suppose you have, for example, a DSL504 ADSL Moden/Router which is a 4 port router (in addition to being an ADSL modem). You've bought a second (perhaps even a wireless) router and want to plug this into the network to share all local machines, and to share the Internet connection. Let's refer to the ADSL router as router A and the second router B.

Configure router A to issue DHCP addresses in some range that does not include one IP address that we will use for router B For example, router A might only issue IP's in the range 192.168.0.2 to 192.168.0.200 and we'll configure router B with 192.168.0.233. This is all the setup that is required for router A, which otherwise will DHCP enabled and its usual WAN setup for your ISP.

Disable DHCP in router B, and configure its WAN to any STATIC IP. Specify a gateway IP of 0.0.0.0 (or perhaps 192.168.111.1). This will stop it sending traffic to its WAN (we won't be using this router's WAN connection). Further configure the WAN Type to be Static with a WAN IP of 192.168.111.2 perhaps (should be different to the A network), and a Subnet Mask of 255.255.255.0.

The LAN configuration for router B should be set to STATIC with an IP address within the subnet of router A but outside its DHCP range. We might set the LAN IP to 192.168.0.233 with a Subnet Mask of 255.255.255.255 and with DHCP Disabled. In fact, router A will serve as the DHCP server for anything connected to router B.

Make sure nothing is plugged into router B's WAN. Connect a LAN ethernet port of router B to a LAN ethernet port of router A to have them talking to each other.

Router \textit{A} Router \textit{B} WAN: --> ISP modem WAN: Empty ethernet Configured for ISP Static IP with Gateway 0.0.0.0 LAN: LAN: IP=192.168.0.1 IP=192.168.0.233 Subnet 255.255.255.0 Subnet 255.255.255.255 DHCP: Enabled DHCP: Disabled LAN Ethernet Cabling: (1) <======================> (1) (2) --> PC1 (2) (3) --> PC2 (3) (4) --> PC3 (4)

That's it!

Now, computers serviced by router B will be assigned DHCP by router A, within the 192.168.0.* network, together with DNS assignments. Router B is just another IP node on A's network. Any LAN computer can access and configure router B by accessing it as 192.168.0.233. All computers will be on the same network subnet and so they will have access to each other for file and printer sharing.