Connecting a wireless router to a switch to an Airtel ADSL modem

When I arrived there was no wireless network here. The Airtel ADSL modem was distributing the wired network to all computers through a switch.

It took me sometime to find out how to do this until I came across this information on how to connect a router to a router:

Suppose you have an ADSL modem with a four port router (e.g., a D-Link DSL504 ADSL Modem/Router or 2Wire 2701HGV-W). You've bought a second router (e.g., a Belkin 54Mbps Wireless 802.11g) and want to plug this into the network to add in and to share more local machines, and to share the Internet connection. Let's refer to the first ADSL router as router A and the second as 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 starting at 192.168.0.2 and ending at 192.168.0.33 and we'll configure router B with 192.168.0.40. This is all the setup that is required for router A, which otherwise has DHCP enabled and its usual WAN setup for your ISP.

Disable DHCP for router B, and configure its WAN (Wide Area Network) type to be STATIC and set it to any IP (e.g., 192.168.111.2--should be different to the A network), with a netmask of 255.255.255.0. Specify a gateway IP of 0.0.0.0 (or perhaps 192.168.111.1, if your router will not allow 0.0.0.0). This will stop it sending traffic to its WAN (we won't be using this router's WAN connection).

The LAN (local area network) configuration for router B should be set to STATIC with an IP address within the subnet range of router A but outside its DHCP range. We might set the LAN IP to 192.168.0.40 (or 10.0.0.137) with a Subnet Mask of 255.255.255.255 (or 255.255.255.254 perhaps if that doesn't work) and with DHCP Disabled. In fact, router A will serve as the DHCP server for anything connected to router B.

Make sure that 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, using the usual ethernet cable that you would use to plug your computer into the router.

Source: http://togaware.com/linux/survivor/Router_Router.html

Although the Airtel ADSL modem 220BX I have here is not a router, it is the one providing the DHCP, therefore, it should be treated as if it was the router itself.

Keep in mind that the switch is a totally passive device and there is no configuration you have to do on it.

The only change I had to do with respect to the information from togaware.com is that the Subnet mask for the network of router B couldn't be 255.255.255.255, or 254, but had to be 255.255.255.0, and I had no problem about it.

Also, it could be a good idea that you assigned static IPs to the computers and laptops that will be connected through the wifi network, otherwise there maybe some IP clashing with the wired computers (as the wifi network is getting IP assignment from the modem, but is not included in the DHCP list).