Your so clueless when it comes to networking.
Really, funny thats not what the reviews say that my boss and the boss above him give me twice a year...
Release and Renew through the IP config only works for dynamic IPs.
Correct....
Most cable companies and anything higher than cable wont work.
Anything Higher than cable??? WTF do you mean???
They usually have very long expiration times on DHCP sometimes for longer than a month.
Really, all the ones I have seen are about a week, sometimes shorter... If an ISP knows they are going to be doing some work, such as re-subnetting changing things like the DNS servers IP or anything like that, they set the lease times even shorter so the CM or CPE will get the new DHCP info quicker...
Imagine, if I was doing an IP clean up because there was a router/CMTS or DLSAM that had 10,000 users on it; then put in a 2nd CMTS to improve services and moved 25-50% off the 1st CMTS, to the second or 3rd or so on...
The scopes for the 1st router would now have a surplus of IPs...
In the current enviorment, ARIN (American Registry of Internet Numbers, the offical body, that all US companies request their IP Blocks from) is really tight on giving out new super blocks, so we really have to use them sparingly.. Till everyone gets IPV6 implemented...
Now, thinking about scopes Times that by Residential CM and CPE address, VOIP CM and CPE addresses, Set Top Box (Cable Box) CM and CPE addresses, Small Buisness Cable Modem CM and CP addresses, etc... Thats a potential for a ton of scopes that either their subnet mask needs to be shortend or changed all together...
If you just changed the interfaces address on the router and the CM or CPEs did not renew their info, it would pretty much break stuff, till people started rebooting or release renewing everyhting...
I would be so nice, if there was a button in the DHCP server appication that would for the clients to release or renew.... But there is no provision for it in the RFC, so I doubt that will never happen, plus it seems like a possible exploit, just waiting to be discovered...
But I guess they could be bumping up the lease times now... I'll have to check... I don't admin the DHCP servers anymore... I just lay out IPs for all the scopes and put them on the routers and CMTS... I mostly work on Cisco hardware...
Some companies also use Static IPs that are tied to the MAC address of the router they lease you or the router MAC that you give them if you already have one.
I haven't seen that done in years... I know AT&Ts @Home Cable used to do it like that before they sold off everything to multiple other cable companies and started offering DSL instead of Cable Modems.... Not sure what they do know as I don't work on DSL...
Even spoofing your hardware MAC wont change anything because it can only be done with hardware in your computer, not the hardware connected to their system.
Every NIC (card), be it a 3com (what I've used mostly) some other brand, or one built onto the motherboard it has a unique 16 digit (0000.0000.0000.0000) mac address...
When the CPE (customers Computer or Wireless router, etc) does a DHCP broadcast request, your cable modem or DSL, does a Unicast request to the GIadder (points to the DHCP Servers address) and the DHCP looks and sees if it has a lease for it or even a static reservation then it give it and address... If it has neither, depeing on how its provisioned it gives it an IP out of a given scope...
You would have to flash the firmware on the leased modem/router or hardware they gave you.
Unless you are talking about the IP of the CM, which I beleive we have always been talking CPEs here, it has nothing to do with the CM, except for the unicast forwarding...
Sadly, for network admins, there are tools out there that people can download that will allow them to change their macs for non legit reasons
like
http://www.klcconsulting.net/Change_MAC_w2k.htm
google it...
and there are a few network tools that have this ability built in for legit testing that if in the wrong hands can be used for the wrong things...