I have a cable modem in one building, but the router is two switches away, the router is not picking up the ip

Question

The router, can't be moved.

Answer 1

Cable modems usually assign IP addresses based on MAC addresses. The modem is trying to communicate with the switch not the router. Also the physical connection would require a crossover cable instead of a straight through because modems are designed to hook directly to a computer or router, not through a switch. Unfortunately you haven't given me a lot of information to work with. About All I could suggest is purchasing a cheap home router from walmart or office max and hook it in between the modem and the switch. Since its a cable modem a regular home router should be able to handle the bandwidth just fine.
A quick note, with this setup you would need a straight through cable going from the modem to the home router and a crossover cable going to the switch. you may also need a second crossover cable between the switches if you don't have an up link port.

Answer 2

what does that mean, "the router is not picking up the ip"? routers don't generally "pick up" ip addresses, they need to be addressed.

if you want the router to be able to route through the cable modem then you need to give the router ethernet interface that connects to the switch an ip address on the same subnet as the cable modems ethernet interface. so if the cable modem's ethernet interface is 192.168.1.1/24 then you would give the router a 192.168.1.x/24 address, and then tell the router that the next hop for it's default route (if that cable modem should be the default route) is 192.168.1.1 or whatever the cable modem's ethernet interface address is.

the switches don't matter, assuming that your not using vlans. i have routers several switches away from my cable modem at home. works fine.

Answer 3

Cat5 cable has a recommended distance limitation of 300 feet. There are repeaters available. Maybe you should connect via fiber instead.

Answer 4

you probably need repeaters to make up for the distance