Connecting Router to a Switch

Posted on 2004-11-24
Last Modified: 2010-04-17

I have a question regarding a router to a switch.  I currently have my modem connected to my router using the uplink port from the router and a patch cable.  My question is do I have to use a crossover cable now to connect the switch to the router?  I looked on the switch but I don't see any uplink port on it.

I had the network all setup, and one day my cable company came to change our cable modem because we changed from a dynamic IP to a static IP address.  I don't know if anyone touched any of the wires, but ever since he came when I have everything plugged in to the network all the lights on the router and switch blink all at the same time, and my network either slows down or crashes.  

The only way I found around this issue is to directly connect to the modem that the cable company sent us then the internet works just on that one computer.

Thank you for your help,
Question by:DaliSalv22
    LVL 41

    Expert Comment

    hooking a LAN port to a LAN port? use a crossover
    LVL 41

    Expert Comment

    also you may have to clone the mac address of the computer that is now connecting (clone it on the router)
    LVL 50

    Expert Comment

    by:Don Johnston
    What type of equipment (brand) do you have for your modem, router and switch?

    LVL 13

    Assisted Solution

    It depends on the router, there is no hard rule here, although every Cisco router I have connected to a switch used a straight cable, but that doesn’t mean there isn’t an exception. Really the only way to know for sure is to try it, if it reason you are asking it because you are worried using the wrong cable might hurt something, rest assured it won’t. Every switch and router now days anticipate in their design having the wrong cable installed, so they won’t be damaged. If they didn’t they have so many returned under warranty it wouldn’t be funny since it happens so often.    
    LVL 11

    Accepted Solution

    You want the modem connected to one router port, and the switch to the other.

    There is, in fact, a hard rule.  Routers and hosts talk at layer 3, and switches and hubs at layer 2 or lower only.  You use a straight-through connection between devices of different layers, and need a crossover between devices at the same layer.

    You might not, however, need a crossover *cable*.  Many small switches offer a port which is either already wired as a crossover, or can be switched to that; a few recent models automatically sense when a crossover connection is needed and switch the port internally.


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