What happens if you plug a router into a modem/router with no configuration?

[Carmen_6]

My father in law has xfinity and they recently updated his modem/router combo to a bigger and faster device. His last setup was still a separate modem and router...

Anyways because of this he still plugged his old outdated router into the new router from xfinity. It's sending out multiple SSIDS, but the connection is constantly slow/dropped. Does having the old router plug in slow the overall speed, or affect anything? I told him that it should be unplugged, but he asked me why, and I really didn't know. Thanks.

 

[bill001g]

It will mostly work unless you get unlucky and the device both use the same lan subnet range then the second router will refuse to activate because it thinks the wan ip conflicts.

The wireless would likely interfere with each other because they use the same radio channels....but if you didn't actually use both at the same time it would be minimal.

You might be limited by the old routers speed if you connect to it but if you connect to the new one the old one would be pretty much ignored.

 

[Pooneil]

What will happen depends on which ports are connected on the old router, LAN or WAN. But with no configuration, there is likely to be two DHCP services running on the network, which can cause problems of duplicate IP addresses or the inability of computers to communicate. Depending on the configurations of the router and the gateway.

A good reason to reuse the router is if he wants to to extend his wifi to an area of his home that gets poor service. If that is what he's doing, the information in this sticky post can help you to help him. If they are just sitting side be side, there is nothing to be gained in normal wifi use.


http://www.tomshardware.com/forum/36406-43-convert-wireless-router-wireless-access-point