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  • Cisco 2811 Router (Newbie Question)

    Hello!
    I usually do not work on our Cisco 2811 router, but I have to add a secondary IP address to it. Here is some background:
    We currently have a T1 from Sprint that connects to the 2811. We have been given 5 public IPs associated with the router (65.xxx.xxx.17 255.255.255.24 and everything works just fine. We had the need for additional public IPs and were given 5 more (63.xxx.xxx.32 255.255.255.24. How do I A) add the secondary IP range to the router and B) make sure that the range of IPs are accessible? Please forgive my extreme ignorance in this matter!
    Thank you.

  • #2
    Re: Cisco 2811 Router (Newbie Question)

    In my humble opinion

    1. Normally 2811 has only two fastEthernet Interfaces.

    2. Company gave you ten ip addresses. this may be called a pool of public ip addresses.

    3. ISP give their clients many ip addresses so they can use it for many networking roles such as web, ftp, mail, vpn etc.

    To which interface you want to configure ip address. IP address will be assigned to the interface where you have connected the cable of CPE.?

    Comment


    • #3
      Re: Cisco 2811 Router (Newbie Question)

      The 2811 router does have only 2 FA ports by default, but there are plug-in compartments where extension modules of various types can be installed, to allow for any number of different types of connection into the single device (serial, GigE, etc.) So multiple connections are possible.

      However, the 2 address ranges are NOT sequential, there's a gap in between them. So they can't both be used on the one interface already used to connect to the ISP's NTE. So I believe the only way to put the second range of addresses into use is to have a second connection to the ISP put in. I know of no way to assign multiple, separate address ranges to a single interface.

      It would help to have more info from the requester regarding what connections already exist to the router, how many clients have traffic passing thru, why they had to request additional public IPs in the first place? Any drawings, dumps of config files or clarifications would be good, here.
      *RicklesP*
      MSCA (2003/XP), Security+, CCNA

      ** Remember: credit where credit is due, and reputation points as appropriate **

      Comment


      • #4
        Re: Cisco 2811 Router (Newbie Question)

        How are you going to use these addresses? Do you want to assign them to the router and map them to private addresses via static NAT, or do you want to create a separate (DmZ) network with these addresses.

        You have several options:
        • add one or more addresses as "secondary" addresses to an existing interface and use static NAT
        • add one address to a subinterface and use 802.1q encapsulation to set up a VLAN on the switch
        • add a new physical interface to the router, assign one address to this interface and set up a physical network using a separate switch
        • route the subnet to a downstream router

        Hard to say which option is the best without further information about your setup. How are the existing addresses configured? Could you post the (sanitized if necessary) running-config from the 2811 router?

        Comment


        • #5
          Re: Cisco 2811 Router (Newbie Question)

          Originally posted by RicklesP View Post
          I know of no way to assign multiple, separate address ranges to a single interface.
          You can add any number of addresses to an L3 interface with the "secondary" parameter (ip address 1.2.3.4 255.255.255.0 secondary).

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          • #6
            Re: Cisco 2811 Router (Newbie Question)

            Thanks for that, Ser Olmy, I hadn't seen that one. I'll make a note. But I still think it'd be good to know more about the setup. I get the impression there may be better ways to fix their network.
            *RicklesP*
            MSCA (2003/XP), Security+, CCNA

            ** Remember: credit where credit is due, and reputation points as appropriate **

            Comment

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