Ooma Telco and Nighthawk CM2100

> I know this is the wrong board to post in.

   I'm pretty confident that a cable modem like the CM2100 qualifies
under "Cable Modems & Routers".

   Sadly, despite Netgear's elaborate claims for its capabilities, it's
a modem, not a router, nor does it incorporate one, so you probably
can't use it for multiple client devices unless you connect it to (only)
a NAT router.

   A quick web or forum search for your (actual) model number should
find abundant reports like yours, from folks who (thanks to potentially
misleading claims) misapprehended the utility of the multiple LAN ports
on the CM2100.

   Visit http://netgear.com/support , put in your (actual) model number,
and look for Documentation.  Get the User Manual.  Read.  Look for "LAN
port".  Do you see anything which suggests any use of ports 3 or 4, or
any use of port 2 other than for port aggregation?

> Ooma worked fine with my Arris Modem.

   What was your "my Arris Modem"?  My guess is that it was a
modem+router (gateway), not only a modem (like the CM1200).