Mac address cloning, was only kind of helpful in the past, with when the MODEMS themselves didnt always easily RELEASE the mac address of what they were connected to before.
EG: if you were modem to PC, then wanted to put in a router.. could be easier to have it clone the PC so it dosnt have to change anything.
Really now a days, the point in moot most of the time.
IF you got the new gateway.. you get it, and connect your PC to it.. will get a DHCP address.
Connect into it, and set it to bridge mode, it will start to reboot. Remove the PC, and plug in the router... modem should latch onto the router, and away you go.
Personally, i have found, that the rogers IP, changes about ever 6 months or so.. so maybe 2x a year, tops.
So while its IS dynamic.. its fairly un-changing.
(i also use free dns service.. with an updater.. so i just always point stuff at the dns address, and its always my right IP)
