Question Modem router isuse

[Kronzee21]

i have a question, I recently switched internet services. From spectrum to att. When I used the spectrum modem it was easy to use my third party router to change my mac address and therefore my public ip address. however now when i try to change my mac address with att what happens is the modem just changes the ip address of my router when i change the mac address. My public IP address stays the same. Why? What is going on here? Please help

 

[drivinfast247]

ATT does not allow you to change it.

 

[kanewolf]

i have a question, I recently switched internet services. From spectrum to att. When I used the spectrum modem it was easy to use my third party router to change my mac address and therefore my public ip address. however now when i try to change my mac address with att what happens is the modem just changes the ip address of my router when i change the mac address. My public IP address stays the same. Why? What is going on here? Please help

What ATT is doing is caller "carrier NAT". There is an ATT router between your "public" IP and the IP on the WAN port of your router.

 

[bill001g]

In most cases att is not doing a actual carrier nat they are doing some thing much more simple even though it kinda is carrier nat. For whatever reason att requires you use their modem/router combo unit. They do this even on their simple DSL connections for some reason.

Att will not even allow you to place their device in bridge mode. They have some really strange method of doing NAT that allows them to use DHCP to pass the public IP to the secondary router but the IP is actually still assigned to the wan port of att router.

Because of this changing the mac address your own router does not do much because it is still hidden behind the ATT router. Even if you could somehow change the mac address on the ATT box from what people who have tried to bypass the att fiber box have found is they actually use a fancy encryption method that uses a unique certificate stored in the ATT unit. They assign the public IP to this encrypted session....in effect they assign the IP to the certificate not the mac. Like most certificate based security it is close to impossible to modify certificates.