EIGRP goes down before line protocol

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Aug 4th, 2010
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Hi,


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I am tying to understand this wierd behaviour when a WAN link goes down.


The below logs are from a cisco 7304 router.


Jul 19 08:31:57.704: %DUAL-5-NBRCHANGE: IP-EIGRP(0)  100: Neighbor 164.55.222.105 (POS3/0) is down: holding time expired


Jul 19 08:32:21.124: %LINEPROTO-5-UPDOWN: Line  protocol on Interface POS3/0, changed state to down


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Jul 19 13:34:40.276: %DUAL-5-NBRCHANGE: IP-EIGRP(0)  100: Neighbor 164.55.222.105 (POS3/0) is up: new adjacency


Jul 19 13:34:41.204: %LINEPROTO-5-UPDOWN: Line  protocol on Interface POS3/0, changed state to up



If you notice when the interface actually went down, Eigrp hold timer expired before before the Line protocol shows down.


Is this behavior expected. Is there a way to fine tune the Line protocol to go down earlier and that trigger Eigrp, rather than EIGRP hold time expiring which would probably take 15 seconds for a OC3 link, hello time being 5sec.


Thanks.

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gatlin007 Wed, 08/04/2010 - 07:51
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If the goal is to cause EIGRP to notice an unreliable link faster than 15 seconds than the hello/hold timers on that link could be adjusted.  This would need to occur on both sides of the link using the interface level 'ip hello-interval eigrp' and 'ip hold-time eigrp' commands.  Something like the following would cause eigrp to declare the link bad after 3 seconds.


int pos x/x

ip hello-interval eigrp 100 1

ip hold-time eigrp 100 3

### 100 is the AS number



Chris

victor_87 Wed, 08/04/2010 - 09:27
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Hello Chris,


Thankyou for your response.


Indeed the Link loss can be identified faster by reducing the hello and Hold timers but we consider 15 sec is ok.


But i was trying to understand how much time a POS interface would actually to identify loss of framing when a link goes down and report a line protocol down on the Log.


In this case it is definitely taking more than 15 secs so thats a lot of time.



Victor

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