Problem with Steam and LAN

[gunner154]

I'm having a problem with setting up a LAN between 2 computers. This problem applies on both infrastructure and network. One computer (A) is Vista and the other (B) is XP. Even with static internal IP set, the computers are able to see each other until Computer A runs Steam. After that, the computers are unable to ping each other. This persists until a certain amount of time (I don't know when) but after a good amount of time, pinging becomes possible. If I were to do anything like run Half-Life or Left 4 Dead, pinging fails again.

BOTH computers have to be restarted in order for pinging to be possible again. However, regardless of whether these 2 computers can ping each other, other computers on the network have no problems pinging either computer (A and B).

More details on how I explored the problem are here:

http://forums.steampowered.com/forums/showthread.php?t=768341

So now, does anyone know what's going on? I want to play some LAN Steam games across the network (notably Counterstrike and Left 4 Dead) but I can't get it working. :( Can anyone help?

[gunner154]

Strangely, the symptoms have changed. Now I can play Steam games on LAN, but whenever I run Left 4 Dead, the same inability to ping occurs.

[Dragoon Knight]

My best guess as to the problem would be that your router is handling Steam improperly.

Say Computer A is running Steam - it connects to the internet, opens certain ports, etc. and your router responds accordingly.  If you try to do the same on Computer B, it's entirely possible that your router is getting confused and refuses to acknowledge that the two can run at the same time; it may think that it's just one client making double the amount of requests, thus not allowing the two to communicate.

It may still allow both to run independently (i.e. connect to the internet and play online) by just queueing the traffic along that port, with no heed as to where it's going.

I'm not sure if you can change the port that Steam uses to connect, but it may be worth seeing if the problem occurs with another router.  Alternatively, it can't hurt going into the Router Setup and ensuring that the hardware firewall isn't buggering about with things unnecessarily.  Good luck, either way.

[gunner154]

I've also considered it to be the router. However the problem now arises only with Left 4 Dead. Even on ad-hoc connection (no router), the same symptoms surface.