Changing the MAC Address doesn't seem to be working?

[bmn1]

So normally I can go into WAN -> Internet Connection -> Special Requirement from ISP -> MAC Address and change this value. Then my connection will go Offline and I have to reboot my Modem. Then after rebooting I will have a new WAN IP Address. Well for some reason this doesn't seem to be working anymore. I've been trying for the last hour and I just can't seem to get it to work using my Router.

The only thing that I could get to work is by unplugging the router from the Modem, then directly connect my laptop to the Modem, reboot the Modem, now I have a different IP Address. But then if I plug my Router back in, reboot the Modem, I'm back to my old IP Address again.

Just to be clear, when I say "IP Address" I'm referring to my WAN IP Address, not my Local IP Address.

I thought maybe my ISP had changed something on their end but since I was able to get it to change by plugging in a different device, then that only leaves the Router to blame.

Router is an ASUS RT-AC87R running on Merlin FW 384.7
Modem is an Arris SB6183
Provider is Cox (suckers) =p

Anyone have any ideas on what else could be causing this or what else I can try?

 

[RMerlin]

Don't just reboot the modem. Some ISPs will require the modem to be turned off 5-15 minutes before they will allow to issue a lease to a new MAC.

 

[bmn1]

Alright I'll give it a try but I'm not 100% sure that's gonna be the issue. When I unplugged my router from my modem and then plugged my laptop directly into the router, all I did was power cycle the modem and as soon as it came online I had a completely different WAN IP. It's very strange, I've never seen this happen before as I've done it many many times in the past without issue.

Is there anything in the firmware that might be causing this? Perhaps I should try downgrading to a really old firmware just to test and see if it still does it or not?