Motorola SGB6580 Wireless Bridge
We recently just got business class internet at home, and they came and replaced our SGB6580 with another modem, and we bought a separate router to go with it. I brought the SGB6580 down to school with me, thinking I could get use out of it, and I'm trying to set it up to where I plug in the live internet into one of the 4 ethernet ports, and then I can connect to it wirelessly or via eth, and I would be assigned an ip like I would if I were plugged directly into the wall, and I would have internet. I got it all set up to where if you plug in something via any of the ethernet ports, the school's servers assign you an ip and you're good to go. I did this by setting the modem/router's LAN ip to one that is valid with the schools network, and then disabled the dhcp server. I also added the MAC address to the "passthrough" box. With the wireless on the other hand though, I can't get it to do the same. I can connect to the network, but it doesn't assign me an ip like eth does. Any suggestions?
Most likely you're running into a security mechanism at the school that only allows one MAC address for a given outlet. Once the modem+router has a LAN IP address of its own, you're spent.
The more proper way to do this is to connect the router's WAN port to the school's network so the WAN IP (and by extension, the WAN's MAC address) are shared w/ your wired and wireless clients behind the router. But now you run into a nasty problem w/ these combo modem+router devices; THEY DON'T EXPOSE A WAN PORT!
Instead, the LAN and internet connection (cable, dsl, etc.) are bridged internally. Makes for a simple, small footprint, easier to configure device (and why ISPs love them), but the downside is that reuse is much more limited.