From: "Frank Haber" 

My cablemodem ISP (RCN NYC) is fairly fierce about manually registering
MACs, blocking 80 plus LANside SNMP-for-DOCSIS, and shutting you off from
your own subnet.  Yet I've had no trouble regegistering a client's
cablemodem or SOHO router with a simple phone call.  I've tried it nine
times now, and never even gotten a grumble out of them.

The big player here (TW), auto-registers new MACs.  It usually takes a
couple reboots and refresh/renews to convince the supervisory software that
you're serious, and have really changed something.

--- BBBS/NT v4.01 Flag-4