Steven Engelhardt

A few days ago, I was messing around with the settings on my Linksys WRT54GL router and moved my home network from 192.168.1.1/24 to 192.168.0.1/24. Changing my mind, I immediately moved back.

Some time later (perhaps after a DHCP lease renewal) I was unable to reach the Internet. Everything looked fine — my connection to the router was working, the router’s connection to the DSL model was working — but I could not reach any websites from my PC. I suspected my DSL connection was down and reset my DSL modem, to no avail.

Today I was preparing to call AT&T and plugged my laptop directly into the DSL modem. I fired up a web browser and, to my astonishment, everything worked!

Assuming AT&T had fixed something on their end, I reconnected my router and tried to access the Internet again. No luck. However, I now knew that the problem was with the router and not the DSL modem.

After a few dead ends (such as cloning my laptop’s MAC address), I took a close look at the results of ipconfig /all:

IPv4 Address. . . . . . . . . . . : 192.168.1.109(Preferred)
Subnet Mask . . . . . . . . . . . : 255.255.255.0
Default Gateway . . . . . . . . . : 192.168.1.1
DHCP Server . . . . . . . . . . . : 192.168.1.1
DNS Servers . . . . . . . . . . . : 192.168.0.1

For some reason, my router was handing out an incorrect DNS server with its DHCP leases! I reset my router’s settings to the factory defaults, but that didn’t help. Instead, I forced the router to hand out 192.168.1.1 as a DNS server and voila, everything worked.

I suspect that when I moved the router to 192.168.0.1/24 and back I triggered a bug in the WRT54GL firmware where it didn’t update the DNS server correctly.

After I got everything working again, I decided to upgrade the WRT54GL’s firmware to a third-party product: DD-WRT 23 SP2. With the exception of a minor hiccup where I had to manually reset the router’s settings after flashing (something I should have done beforehand), DD-WRT is working flawlessly.