Could this wireless set up cause this issue?

Question

I have two routers hooked up to a DSL modem. The first is an older Linksys wired router(might be BEFSR41) and the other is a newer Cisco Valet M20. The valet was added on recently to enable WiFi support for mobile devices. Recently, I've seem network problems in which about every minute all computers on the whole network, both WiFi and wired, get their internet connection aborted for 30 seconds after which it comes back. Just randomly, the Valet was turned off one day, and it seems the problem does not exist anymore.

Diagram:

I'm not sure what this problem is, but I can't seem to understand why/how the Valet would be able to affect the connection of computers not even connected to it. Is there an explanation that can prove the Valet could be causing this or is it just a symptom of another problem?

Answer 1

If you have DHCP servers active in both the Linksys (or modem) and the Valet, then that would be a problem. The Valet should have its DHCP disabled (assuming that the Linksys is connected directly to the ADSL modem) and should be configured to act as a wireless access point with a static or reserved IP address, not a wireless router. Otherwise you have race conditions and contention between two routers, resulting in unpredictable behavior.

You should setup the Valet similar to the 2nd wireless router in this article, but just ignore the 1st wireless stuff. The salient steps are assigning a static IP address to the LAN side of the Valet, excluding that IP address from the DHCP range, and configuring the Valet as a wireless access point.

In your current setup, you have to make sure that your two routers are properly configured to play nice with each other. You cannot just plug another router (that has DHCP enabled by default) into your network. For a simpler setup, you may want to reconfigure your network so that the Valet is the wireless router connected to the modem, and add a switch if you need more wired ports. This simple configuration would have just one wireless router (the Valet) and a (plug-n-play) switch (that does not require any configuration).