I have a netgear g54 WGR614v10 wireless router and I'm switching over to Cox which require DOCSIS 3.0. Alleigance and AT&T didn't which surprises me (unless my router already uses DOCSIS 3.0 then that's okay)
Generally, routers are not specifically DOCSIS compatible, a cable modem would be though. The router should work with the modem, which is usually supplied by Cox.