I'm pretty sure that I've missed out something really, really obvious here, but my laptop no longer resolves domain names, for some reason. By typing in the IP of google.com, I can view the website, so it's not a connectivity error. This is on a Gentoo system using a 2.6.9 kernel.

For a few days, our network went down, and when it came back up, my desktop was resolving domain names, but my laptop couldn't.

After I discovered that things weren't working, I removed net.eth0 from rc-update, and tried setting up the network manually.

I've tried the following commands (we're using a static ip setup here, gah)
ifconfig eth0 192.168.123.249 netmask 255.255.255.0 broadcast 192.168.123.1 up
route add default gw 192.168.123.1

Have I missed out something really, really obvious?

What does /etc/resolv.conf look like? That would be the file you may need to add your name servers to. You should have something similar to this in the file.

nameserver xxx.xxx.xxx.xxx

Where xxx.xxx.xxx.xxx is the ip address of your dns servers.

good luck.

resolv.conf has the correct address. sorry, I should have mentioned that beforehand.

What is the network topology, and how are you connected? Does /etc/resolv.conf contain the ip address of the gateway machine or the actual dns servers ip's from your isp?
good luck.

It's curiously started working again. Strangeness. I will investigate further.

I don't recall ever seeing this problem, normally it either works or it doesn't, not intermittantly. Some googling might produce some explanation, but, since it's working I'm glad you're sorted.
good luck.