bill001g :
The problem you have is your are confusing term. It the device is a DSL "MODEM" then it does not use IP address so it is purely a layer 2 device....well sorta. If it does anything with IP addresses it is a "ROUTER" which makes it a layer 3 device.
DSL is a really bad example to try to discuss OSI layers. Now you still have a physical layer on the DSL but the layers above that are based on ATM which does not follow the standard OSI concept. It actually has a bunch of layers that make up what would be considered layer2.
ATM used to be very popular years ago but you now seldom see it used in anything except DSL.
Thanks for replying.
Yeah I was trying to discuss the part of a
normal 'DSL modem' after the actual modem part. (The part the deals with the communication with the device connected to it). Not DSL.
So your saying these normal modems with an ethernet port communicate with the connected device over layer 3? This makes perfect sense to me for a router that gives the device a private IP address via DHCP then the default gateway as the modem's IP address.
Although what I do not understand is how a modem can allow the connected device to use the public IP address assigned by the ISP. (Which I understand some do?) How does the computer know to send all internet traffic to the MAC address of the modem without IP?