Some new ones are Both I read.
Here is info that someone else got told on a VM forum.
QUOTED :
" There's a big difference between a cable router and an ADSL router.
Firstly, a router is a device to connect 2 networks - in the case of a home router it connects your internal, private network to "the internet" network.
A wireless home router is more than just a router, it combines a router (to connect to the outside world), a switch (to connect your PCs to each other) and a wireless access point (to link wireless devices to the switch and then on to the router)
In the case of an ADSL router, it also contains an integrated ADSL modem, so will not have an ethernet WAN port, it will have the telephone line connector instead. If you have an ADSL modem with an ethernet port you can use a "normal" cable router as your router, just hook this into the WAN port.
If you connect your cable modem to one of the LAN ports on an ADSL router and then hook up the other PCs on your netowork there is NO routing going on. First I am surprised it works at all (it probably won't if you connect more than 1 pc), second you are opening up a massive security hole.
You have NO private network right now if you have connected the modem to one of the LAN ports.
Unless your model has an RJ45 WAN port, clearly marked as "WAN" or "Internet" you cannot use it to connect to your cable modem. "