eigrp neighbor flapping

Unanswered Question
Feb 25th, 2009
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Hello all,

i am facing one acute eigrp problem , getting error as below ,

%DUAL-5-NBRCHANGE: IP-EIGRP(0) 100: Neighbor (Vlan10) is down: retry limit exceeded.

Could any one solve my problem.



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Overall Rating: 4 (1 ratings)
maahiraahi Wed, 02/25/2009 - 06:50
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conf on

interface Vlan10

ip address

ip helper-address

no ip redirects

no ip unreachables

no ip proxy-arp

ip pim sparse-dense-mode

ip cgmp

no ip mroute-cache

load-interval 60

standby 2 ip

standby 2 priority 105

standby 2 preempt

arp timeout 28800

router eigrp 100

redistribute connected

redistribute static


no auto-summary

ip route

conf on

#sh run int g0/0

Building configuration...

Current configuration : 248 bytes


interface GigabitEthernet0/0

ip address

no ip redirects

no ip unreachables

no ip proxy-arp

ip flow ingress

duplex auto

speed auto

media-type rj45

service-policy input Cos_in


router eigrp 100

redistribute connected

redistribute static

redistribute bgp 65000


default-metric 2000 10000 255 1 1500

no auto-summary

no eigrp log-neighbor-changes


maahiraahi Wed, 02/25/2009 - 07:13
User Badges: - its a router running bgp for WAN and eigrp for lan. - its a L3 sw , running EIGRP for lan.

both are directly connected.

neighbour flaps every 1min 20 sec.

%DUAL-5-NBRCHANGE: IP-EIGRP(0) 100: Neighbor (Vlan10) is down: retry limit exc


%DUAL-5-NBRCHANGE: IP-EIGRP(0) 100: Neighbor (Vlan10) is up: new adjacency

think this will help u out.

lamav Wed, 02/25/2009 - 09:55
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Under vlan 10's SVI, I see you have and the neighbor is supposed to be Is that a typo under the vlan 10 interface?

Also, I see that you have a QoS policy applied to the neighbor interface, are you sure that the eigrp hellos are not being dropped to allow higher prority traffic to use that link?

You may want to isolate the problem to either a network issue or a higher layer problem with the hellos themselves. If it fails every 120 seconds, can you run an extended PING between routers to see if it fails?


DialerString_2 Wed, 02/25/2009 - 14:47
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  • Bronze, 100 points or more

If you hello timer are different your adj will flap. Try hardcoding them on both sides. Check your cables if you haven't already

maahiraahi Wed, 02/25/2009 - 20:36
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Ping response is ok from router to switch. mtu is 1500 on both the side.

maahiraahi Wed, 02/25/2009 - 20:42
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observing SRTT 0, Any clues?

#SH IP EIGRP INTerfaces G0/0

IP-EIGRP interfaces for process 100

Xmit Queue Mean Pacing Time Multicast Pending

Interface Peers Un/Reliable SRTT Un/Reliable Flow Timer Routes

Gi0/0 2 0/0 0 0/1 50 0

You said it started to do this 2 days ago - but before this everything was OK.

So what changed 2 days ago - EIGRP after being configured and forms a good neighbour does not suddenly stop working unless something has changed, either in config or physical or connectivity.

Check the logs to see what happend the time it started to flap.

maahiraahi Sat, 02/28/2009 - 03:33
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veriried, But didnt get any clue.

Then suspected Lan cable as it was about 50m long. chanbged it,then its started working fine.

looks strange, as i didn't see any packet drops on the interfaces , mtu fine, ping response was fine .

Lost option was to change the cable.

any way thanks every one.




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