What do I have to do to see my server on LAN tab?

[wtfsrcds]

This question applies to both hl2mp and cstrike, but for simplicity I'll just say cstrike. This is a fresh installation, no mods. No matter what I do, the LAN tab always says "There are no servers running on your network"; I always have to go to Favorites and enter the IP address manually (my server does also show up on the Internet tab).

OS: Ubuntu 9.10 32-bit
CPU: Intel Core Duo 1.8GHz (dual core, no HT)
RAM: 2GB

Command-line: ./srcds_run -game cstrike -insecure -ip 192.168.0.15 +map de_dust -autoupdate
server.cfg:

Code:

hostname MyServer
sv_password foobar
sv_lan 0

The value of sv_lan does not seem to have any effect...