Need help QUICK

Posted on 2006-03-25
Last Modified: 2010-03-19
I have a Cisco 2600 router connecting to a cable modem. Cable tech support says interface has to be configured to pull ip from them automatically. How does this setup? What's the syntax I should be using?
Question by:wrt1mea
    LVL 11

    Accepted Solution

    This is the command to do that.

     interface Ethernet 1
     ip address dhcp

    Additionally you can specify a client id and hostname.

    You can read about it here.


    LVL 1

    Author Comment

    I did this and it still isn't pulling from the ISP.
    LVL 32

    Expert Comment

    Call up your ISP and tell them that you've configured it on your part. Thats only thing to do on the router. Additionally you could go to Interface ethernet1 and issue a 'shut' and a 'no shut' to see if it fetches.

    I believe cable modem is already in bridged mode ?

    LVL 18

    Expert Comment

    by:Sam Panwar

    Expert Comment


    What is your exact problem? Only assigning an IP address to the cisco's port from the DHCP server of the cable modem?? Or you mean to access internet from any host in the local network.

    What is the topology of your network? If your problem is only assigning the IP address here is my comments:

    Be use that your interface has the following configuration:
    interface Ethernet x
     ip address dhcp
     no shut

    By default, Cisco interfaces are in shut-down state. That might be the problem if you have configured properly. If you have already issued "no-shut" command in the configuration mode and still you have problem; you can post the output of the:
    #show run
    #show ip interface brief

    commands in order to receive proper solutions.

    OR you can give a static IP address to your router's interface although the cable modem is running a dhcp server. Assuming your cable modem's ethernet interface has the IP address: with mask;
    interface Ethernet x
     ip address  
     no shut

    (assuming no other host is using this address. better to check from the cable modem by issuing a ping command. You can use any address from .2 to .254)

    Also keep in mind that if your router already received the IP address you may have other problems (depending on the topology) especially you should have to setup correct routings (static or any dynamic routing between cable mode and cisco).


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