You should not have any problems playing Half-Life through the Linksys Etherfast Cable/DSL router (BEFSR41). By default, this router will allow any outbound traffic. Assuming your network is set up correctly, and the router too, this is truly plug-and-play.
If you are planning on having several (legal) copies of Half-Life playing internet games at the same time, you will run into on smaller issue. They all have to have a different source-port. And here's why: All connections from a half-life client (your computer) to the server comes from port 27005 with a destination of 27015. The server will see you coming from the routers IP address (say 22.214.171.124:27005). If you attempt to have multiple sessions from you LAN to an internet server, all the connections will be coming from 126.96.36.199:27005. Naturally, this will not work. Therefore, the solution is the change the source port of the clients on the LAN so that they are all different. This can be done either in the console by typing "clientport 2700x", or by adding a small line to the command-line that you use for starting half-life.
D:\SIERRA\Half-Life\hl.exe -console -zone 1024 +clientport 27004
Many people are reporting problems when trying to run a server from behind a Linksys box. After a couple of minutes, the clients will be disconnected with what appears to be a corruption problem. I wish I had the answer for you people, but I don't. This is probably another firmware problem that Linksys will have to figure out. So, I'll reverse my previous statement and say: You may not be able to run a Half-Life server from behind a Linksys box.
© 1999 - 2004 Lars M. Hansen