FA0/0 Always Freezing with status and protocol up

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Aug 12th, 2010
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Hello House, Awz the Networks at ur side of th world? Pals, I have a slight challenge on my network on of my Border Routers for INternet Traffic. The Fast Ethernet Always 'Freeze' technically. (The Status and Protocol is always UP-UP), but I can not connect to the next hop, thus loose connectivity to the internet. All I do to solve this problem is simply to shut the interface and bring it back up, with the 'shut' and 'no shut' command. The frequency occurennce is increasing by the day. My team and I and suggesting we change the Interface card, but I fear the problem might still persist. I hope to hear your opinion, suggestions and pieces of advise.

I did a Sh Ip int for the said interface when it frooze  and after I brought it back up

Thanks Oluwunmi

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u1kumar2002 Thu, 08/12/2010 - 03:21
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    As per your query, I understand you have a border router which is connecting to internet by fa0/1 interface and every time the status and protocol is up after the link goes down then also you can see the status and protocol is up.

This is because of fa0/1 is connecting to some switch of ISP and the link failure is not in between fa0/1 and that switch. The link failure may be happened after that switch. That time fa0/1 will be up , since the connected interface is not down.

but here you can verify by routing protocol , Suppose you have BGP or any dynamic routing protocol the neighborship will be down as the link fail.

Interface will not show down till the next hop switch will go down...

here is diagram which will help you for understanding...

Router fa0/1------> ISP switch ---------> POP -----------> CORE-------> INTERNET

in this network till the time your ISP switch is up your interface will be up, your other end IP will be configured on POP or CORE.

So you can't ping the other end IP but then also your interface is up..

hope this information will help you....

Do rate for helpful suggestions...



philip moore Thu, 08/12/2010 - 03:48
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agree that this is very likely a L2 issue.

you could try to find the mac address of the directly connected ISP switch. Then check the mac address table to see if you are getting incompletes for this and other addresses.

Next time it occurs, try clear mac-address-table instead of shut/no shut. I'll bet it probably has the same affect as shut/no shut.

I would also try another interface on your device, and try changing the cable - sometimes odd behaviour can happen if if the interface shows up/up.

Of course, raise a support request to your ISP for assistance.

k_srinadh Thu, 08/12/2010 - 05:01
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As per yous inputs,its conneted to ISP..Check following

* If BGP is conficured check status of BGP using show ip bgp summary

*Change LAN cable which is conected to your Border Router.

* First Configure another FE interface..If problem still persists..Log a complaint with ISP by mentioning the Problem

Hope this Helps.



Tharak Abraham Thu, 08/12/2010 - 05:43
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Please have a look at the counter of the interface ?

Any errs ?

Any oversubscription ?

If No, please open a TAC case with Cisco and get it rectified !


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