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must routers be on the same network ?

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  • must routers be on the same network ?

    Hi guys


    There are two routers that connecting to each other with leased line. Following picture describe this.

    Click image for larger version

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    my question is :

    must it be same network s0 and s1 interface's ip address ?. is this mandotory ?. is it possible that ; ip address of s0 is 150.50.50.250 /32 and ip address of s1 150.50.50.8/24.( A and B router uses EIGRP protocol)

  • #2
    Re: must routers be on the same network ?

    yes, they have to be on the same network. if they weren't, they would need a router to route between the networks--which is redundent

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    • #3
      Re: must routers be on the same network ?

      thanks.
      But imagine that so's ip address is 100.50.50.250/32 and s1's ip address is 100.50.50.15/32;

      in this case do a and b routers run properly?

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      • #4
        Re: must routers be on the same network ?

        A 32 bit subnet mask is a nonsense; it doesn't allow for a "host" portion of the ID. It's not a valid address. Did you do that deliberately?


        Tom
        For my own and your protection, I do not provide support by private message under any circumstances. All such messages will be deleted and ignored.

        Anything you say will be misquoted and used against you

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        • #5
          Re: must routers be on the same network ?

          Originally posted by abdullahliv View Post
          thanks.
          But imagine that so's ip address is 100.50.50.250/32 and s1's ip address is 100.50.50.15/32;

          in this case do a and b routers run properly?
          No, for two reasons.

          1, like metioned, a 32 bit subnet mask won't allow any bits for the hosts. The minimum you can use is 30, which would leave 2 host addresses. (This is used for point-to-point wan links)

          and 2:
          Assuming you meant /30 the the serial interface with the ip 100.50.50.250 would be an a different network than the serial interface with the ip 100.50.50.15. Because they are on different networks, you need something to route in between them.

          What WOULD work is router1-s0=100.50.50.250/24 and router2-s0=100.50.50.15/24

          this would put all hosts that start with 100.50.50.x to communicate with each other without the need for a router.

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          • #6
            Re: must routers be on the same network ?

            With a point to point link there are ways to do this with no addresses - look at ip unnumbered. If you are going to address it though then you need a valid /30.

            To the other poster that says /32s are invalid/nonsense/etc, this is incorrect. These are generally used for loopback addresses and for granular host routing.
            Thanks,
            Brian Desmond
            Microsoft MVP - Directory Services
            www.briandesmond.com

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