1 Reply Latest reply: Mar 22, 2009 4:41 AM by Scott Morris - CCDE/4xCCIE/2xJNCIE RSS

    Connected Route Issue

    Daniel Khouri

       

      Please find attached a screenshot on a network im working with on packetracer.

       

       

      Quick run down on the layout - I've assigned a network range for each connected router and enabled EIGRP (without no auto-summary yet).

       

       

      Here's the problem.......

       

       

      When im on R1 and do a show ip route, I get the following

       

       

      192.168.10.0/24 is variably subnetted, 4 subnets, 2 masks

      C 192.168.10.8/29 is directly connected, FastEthernet0/1

      C 192.168.10.16/29 is directly connected, FastEthernet0/0

      D 192.168.10.16/30 via 192.168.10.10, 00:33:08, FastEthernet0/1

      D 192.168.10.28/30 via 192.168.10.22, 00:33:08, FastEthernet0/0

       

       

      I can understand the router seeing 192.168.10.8/29 as being directly connected because it is but how come it's showing

      C 192.168.10.16/29 is directly connected, FastEthernet0/0 ??

      Shouldn't it be showing 192.168.10.20/29 instead?

       

       

      Since R1 is showing 192.168.10.16/29 as being directly connected, when I hop on R2 and do a show ip route, I get the following

       

       

      192.168.10.0/24 is variably subnetted, 3 subnets, 2 masks

      D 192.168.10.8/29 via 192.168.10.21, 00:39:21, FastEthernet0/1

      C 192.168.10.16/29 is directly connected, FastEthernet0/1

      C 192.168.10.28/30 is directly connected, FastEthernet0/0

       

       

      It's not showing the 192.168.10.16/30 EIGRP range because it's see'ing 192.168.10.16/29 as being directly connected.

       

       

      What am I doing wrong!!!! arghhhh

       

      Cheers.

      Daniel

       

       

        • 1. Re: Connected Route Issue
          Scott Morris - CCDE/4xCCIE/2xJNCIE

           

          Actually, your problem is very simple... Whoever created the diagram messed up with the bit boudaries.

           

           

          You have in the diagram:

           

           

          R1-R2 Link = 192.168.10.20/29 (using .21 and .22)

          R1-R3 Link = 192.168.10.8/29 (using .9 and .10)

          R2-R4 Link = 192.168.10.28/30 (using .29 and .30)

          R3-R4 Link 192.168.10.16/30 (using .17 and .18)

           

           

          Now... A /30 uses 4 Ips (well, ok, two usable plus network/broadcast) and a /29 uses 8 IPs (6 usable, blah, blah, blah)

           

           

          So your valid /30 networks could be:

           

           

          .0, .4, .8, .12, .16, .20, .24, .28, .32, etc.

           

           

          Your valid /29 networks can only be:

           

           

          .0, .8, .16, .24, .32, .40, .48, .56, .64, etc.

           

           

          So your R1-R2 link is REALLY 192.168.10.16/29 but fortunately, .21 and .22 still happen to be in that range.

          In the meantime, R3-R4's link as a /30 REALLY does work.

           

           

          Even though you'll have a connected and an EIGRP route, the most-specific routing will still always win!

           

           

          in a route-table lookup, the most-specific match is done BEFORE any AD/Metric comparison.

           

           

          Try looking at "show ip route 192.168.10.17", "show ip route 192.168.10.18", "show ip route 192.168.10.21" and "show ip route 192.168.10.22" output. Even though they all are PART OF 192.168.10.16/29 you'll find different info.

           

           

          HTH,

           

           

          Scott

          smorris@internetworkexpert.com