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This Question is Not Answered 1 Correct Answer available (4 pts) 2 Helpful Answers available (2 pts)
3987 Views 1 Reply Latest reply: Mar 22, 2009 4:41 AM by Scott Morris - CCDE/4xCCIE/2xJNCIE RSS

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Connected Route Issue

Mar 21, 2009 11:21 PM

Daniel Khouri 15 posts since
Aug 16, 2008

 

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 Connected Route Issue via 192.168.10.10, 00:33:08, FastEthernet0/1

D 192.168.10.28/30 Connected Route Issue 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 Connected Route Issue 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

 

 

Attachments:
  • Scott Morris - CCDE/4xCCIE/2xJNCIE 8,398 posts since
    Oct 7, 2008
    Currently Being Moderated
    1. Mar 22, 2009 4:41 AM (in response to Daniel Khouri)
    Re: Connected Route Issue

     

    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

     

     

     

     

     

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