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WAN links goes down simultaneously

slk_iocl
Beginner
Beginner

Hello everyone,

                               I have a router with 2 WAN links from two different ISPs terminated on Serial & Gig interfaces. Both the interfaces are in different network. Traffic on both the links are handled by QoS. BGP is the protocol. The issue is whenever one link from an ISP goes down the other too goes down at the same time and it happens always when the link connected to Gig i/f fails , then the link connected to Serial i/f too goes down and not vice-versa. Remedial actions like restart router , changing of i/f , restarting the MODEM , etc doesn't always resolve the issue.Even tried replacing the router. Replicating this condition is not sucessful. It looks as if it happens randomly. 

The router & image file info is :: flash0:c1900-universalk9-mz.SPA.152-4.M2.bin

Can somebody throw any light on this?

 

5 REPLIES 5

tyroneclark871
Beginner
Beginner
Hi,

Can you attach the running-config here?

Yup...running config attached.

Jaime Valencia
Hall of Fame Cisco Employee Hall of Fame Cisco Employee
Hall of Fame Cisco Employee

This is the Unified Communications area of CSC, might want to move your post to a relevant forum.

HTH

java

if this helps, please rate

chrihussey
Collaborator
Collaborator

Hello,

Considering the differences in bandwidth / throughput capabilities is it possible that the serial interface simply gets saturated when the Gig fails? 

1- What is the normal amount of traffic on the Gig interface?

2- Is the interface up, but BGP peering just fails.

3- If the interface is indeed down/down and nothing you do works on your side, it may be on the provider side. Perhaps contacting them when it ossurs may provide resolution / answers.

4- Is logging enabled on the router so that when it occurs again there may be some indications as to what is happening?

Hope this is of some help.

 

Thank you chrihussey. 

I reply to you by points...

1.differences in bandwidth / throughput capabilities - BW differences exists in other places as well . But I don't see this type of issue there. Atmost the other link would get choked with heavy Tx/Rx load. But the line protocol would not go down

2.What is the normal amount of traffic on the Gig interface? - around 60% of load

3. If the interface is indeed down/down and nothing you do works on your side, it may be on the provider side. Perhaps contacting them when it ossurs may provide resolution / answers. -  Almost all the time the ISP response would be " router/port fault...our side has no problem" :)

4- Is logging enabled on the router so that when it occurs again there may be some indications as to what is happening? - Yes , but a simple "interface IP address 172.38.x.x is down " !!

I have changed the interface port in two routers in the past one week and observing the link and it is so far so good. But as I said in my first post the condition cannot be simulated as it seems to be happening randomly . So , I'm not able to locate the problem area... hardware , IOS or ISP? 

 

 

 

 

 

 

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