Configuring Linksys WRT54GL for a larger network

I have a passion for computer networks and configuring of network equipment and services. At home, both at my parents house and in my appartment, I have set up networks suitable for medium to large corporations. I run my own servers for DNS, DHCP, Web, Mail, printer and file sharing, databases and central authentication for wireless users.

I just bought a Linksys WRT54GL v1.1 wireless router that I will set up at my parents neighbors house, where my grandmother lives. My sister just moved in there and want Internet connection.

I have stretched CAT-6 Ethernet cable between the houses to give a stable network connection. This is a danger for data equipment in cases of lightning and other power faults. Therefore I bought an UPS from APC with surge protection for both power and network cables. I also saw the possibility to put up wireless network there, which is great to have when we are visiting my grandmothers house, for example at Christmas. Oh, yes, I am adicted to Internet.

System information about the routerOne of the first things I did with the new router was to install OpenWRT WhiteRussian, as an alternative firmware to the ones from Linksys. I found this firmware somehow featureless and thought of going back to Linksys firmware. Luckily I found DD-WRT which is based on the core of OpenWRT. This firmware had most of the features I was could think of, so I decided to go for this one, version 23 SP2.

Setup of IP addresses and DHCPI wanted a configuration where the router could send packets back and forth between the interfaces on the router, not only work as a NAT enabled Internet gateway. I am not very often home at my parents, because I live in Drammen, so I have to be able to remotely control those computers behind the router if anything should fail. I changed the DHCP service on the router to forward DHCP requests to my FreeBSD router in the house of my parents. The FreeBSD router runs a DHCP service, and that way I will have a centralized configuration point for IP addresses on my network. I configured a new /24 subnet in my DHCP service to be used on the router in the house next door.

Deactivated the SPI firewallDD-WRT has per default an active SPI firewall that filters all packets from the WAN interface that tries to establish a connection to computers behind the router. I had to deactivate this firewall to let the router pass DHCP response packets back from my DHCP service to the clients. I configured a static route on my main router at my parents house for the new /24 subnet to be routed via the WAN interface on the Linksys router.

It is important that the Linksys router receives a static IP address on the first subnet, the one at my parents house, because that is necessary to keep the static routing stable over time. I did this by configuring the DHCP server to give the Linksys router a static IP address.

This is a translation of my norwegian blog post over at