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EIGRP isue

Posted on 2009-02-19
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Last Modified: 2012-06-21
Attached diagram is my scenario ...
In order for the primus router to reach Verizon, there should be 2 routes in the routing table (or EIGRP topology table)
1. Via the Metro Ethernet link
2. Via AAPT through to metro ethernet to Verizon ;

but I see only 1 route which is the second one (Via AAPT). If i would shut/no shut the interface on primus router (i.e WAN 172.16.0.82/28),then it would get that entry in the routing table directly via metro ethernet; only until EIGRP dead timer after which it recieves EIGRP goodbye message and entry is not there in routing table anymore. So what I have to do is to shutdown the link between AAPT and Primus and now I can get entry from Primus to Verizon subnet directly via Metro ethernet.
Now, when I didnt had the link shut down, on my primus router, i was only getting entry of Verizon's subnet (203.x.x.x subnet) and no second entry was there in the topology table. Ideally, It should have had another entry saying that directly connected link between primus and verizon was backup entry but it was not...
Attached is a zip file showing scenario diagram and my topology. if am not able to explain the problem, please let me know ....

Verizon.txt
AAPT.txt
copy.JPG
Primus.txt
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Question by:nabeel92
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by:donmanrobb
ID: 23688338
Please post the output of "show ip eigrp topology"
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by:nabeel92
ID: 23688412
Primus#sh ip eigrp topology
IP-EIGRP Topology Table for AS(1)/ID(172.16.0.82)

Codes: P - Passive, A - Active, U - Update, Q - Query, R - Reply,
       r - reply Status, s - sia Status

P 10.0.9.0/24, 1 successors, FD is 261376
        via 172.16.0.81 (261376/258816), FastEthernet0/0
P 10.0.16.0/24, 1 successors, FD is 30720
        via 172.16.0.81 (30720/28160), FastEthernet0/0
P 10.0.20.0/24, 1 successors, FD is 28160
        via Connected, Vlan1
P 203.166.28.32/29, 1 successors, FD is 30720
        via 172.16.0.83 (30720/28160), FastEthernet0/0
P 172.16.0.80/28, 1 successors, FD is 3072
        via Connected, FastEthernet0/0
P 172.16.0.76/30, 1 successors, FD is 642560
        via Connected, FastEthernet0/1
P 172.16.0.72/30, 1 successors, FD is 30720
        via 172.16.0.81 (30720/28160), FastEthernet0/0
P 172.16.0.64/29, 1 successors, FD is 261120
        via 172.16.0.81 (261120/258560), FastEthernet0/0

I'll reexplain the prob as i think i made it a bit complex to understand ... Primus should be able to go verizon directly through the metro ethernet (Layer2) right ? it doesnt .. It goes via AAPT instead ... Another strange thing that happens is that the primus router tries to establish eigrp neighbour adjacency with Verizon directly thru that layer 2 interface but eventually it says "EIGRP good bye recieved" and hence only path it uses is via AAPT .... this happens at a constant interval (say every 3 or 5 minutes) ...

Right now, ive shut down the interface directly connected interface between Primus and AAPT and then only I see a stable EIGRP entry directly from Primus to Verizon ... If I had it on, then EIGRP would select it as best path and EIGRP route flapping would start occuring on that Layer 2 direct link between Verizon and Primus ..... The above output is after shutting down that direct link b/w primus and AAPT...

Link cost: All Metro ethernet links are 4 MB.
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by:donmanrobb
ID: 23693377
I'll set this up in my lab and get back to you tonight
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by:nabeel92
ID: 23706980
any update on that 1 mate ! !~
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by:donmanrobb
ID: 23707205
Didn't notice any issues with the configs themselves. But I haven't had a chance to load it up to see if the same behavior happens. You said if you shut down the AAPT link you get the adjacency between Primus and Verizon? Does it go down after a couple minutes?
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by:nabeel92
ID: 23707240
no, it doesnt go down ....
rite now, the link between aapt and primus (172.16.0.76/30) is shutdown and Primus is sending traffic to Verizon Subnet (203.x.x.x) via 172.16.0.83 path .... However, If i noshut that above link between AAPT and Primus, i get into this problem of eigrp route flapping as mentioned above; where

1. Primus goes to Verizon via AAPT instead of going directly thru the 172.16.0.80 network

2. On the Primus router, the EIGRP entry for 203.x.x.x subnet keeps coming in/coming out in the routing table through 172.16.0.83 subnet .... one minute, it would be there, next minute it wont be .... and so on..
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by:donmanrobb
ID: 23712157
Try adding something like bandwidth 10000 on the Primus -> Verizon interface and see if the issue still occurs.
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by:donmanrobb
ID: 23712174
And now that I think about it, try adding no ip split-horizon eigrp 1 on the Primus->Verizon interface.
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nabeel92 earned 0 total points
ID: 23712581
actually i got the issue fixed...silly mistake i made .... the 172.16.0.80 subnet i configured on AAPT router was /29...i changed it to the correct one i.e. /28 and it was fine and i know now why that happened ... aapt was advertising 172.16.0.80/29 to primus via 172.16.0.77 and primus had a directly connected 172.16.0.80/28 as well ; since most specific routes takes the precedence so i think thats why it was taking the first one into consideration and not the second one ... but anyhow, its been fixed ...
Thanks a lot for ur support ;)
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