M2 connection

Sorry about that.

Your MR2100 is a modem/router that manages all the traffic on your local network. A bit like a traffic cop.

If you add another router, then you end up with two traffic cops. Stand back and watch everything grind to a halt.

One way around that is to turn off the router bit of one of those devices. Your MR2100 or the second one you mentioned.

Some modem/routers have a simple built-in setting that does the job for you. (It often goes under the label "bridge mode".) Then your second router plays the good cop role.

I can't see an easy way to do that on the MR2100.

Another way to keep the traffic flowing is to turn off the router bit of the second router and plug it into the first modem/router. Your MR2100, which then becomes the good cop.

Then you can use the second router as what they call a wireless access point (AP). Most of the routers I have played with make it easy to turn off the router bit of the second router

It really isn't that complicated. Unfortunately, it can be impossible to work out what is going without a little bit of head scratching.

Maybe there's a neighbourhood nerd who likes playing with these things.