Why do modems require IP addresses?

[o2fst4uo]

As in the title, why do modems have IP addresses? Is it purely for Web based management? As far as I understand modems, they should only operate at layer 2 of the OSI model shouldn't they? Translating Dsl (or whatever bearer you use) to ethernet.

I have an ac66u but I can't use it because I don't have a modem only to connect it to (here in NZ we normally only use modem/routers rather than seperate devices) so I'm shopping around and am just a bit confused about modem IP addresses because I'm well aware of the issues that come with double NAT.

Thanks in advance. And please move this if it is in the wrong place.

 

[azazel1024]

Yes, the IP address is only for the management console. Just like semi-managed and managed switches. You can have completely dumb, unmanaged cable modems with no management interface, in which case they have no IP address, those just aren't the most common type.

 

[o2fst4uo]

Sweet thought so. Saves the confusion of choosing a modem then.

Second question though, is the management interface accessible while inside your lan? The router would have a public IP on the wan side and wouldn't be able to route to a private IP on the wan side wouldn't it? Do you have to unplug and directly connect to change any settings?

 

[Nerre]

You can set up a routing rule to be able to access the modem from the LAN. There are topics in this forum about it.

 

[darla]

Not an expert on this stuff but isn't the registration done via the MAC address of the modem?

In my experience with Comcast I always have to verify the MAC address with them.

If its a modem only it doesn't do DHCP.
The larger boxes have Modem with a build in router as if you would have connected your own one to the modem only. The difference is that they can remotely control it if needed.


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[stevech]

Sweet thought so. Saves the confusion of choosing a modem then.

Second question though, is the management interface accessible while inside your lan? The router would have a public IP on the wan side and wouldn't be able to route to a private IP on the wan side wouldn't it? Do you have to unplug and directly connect to change any settings?

many cable modems (5 I've owned) can be accessed as 192.168.100.1 even if that's not your normal 192.168.1.x subnet.