Link reliability brings down the entire multilink

Unanswered Question
Oct 29th, 2008

Hi All,

We have 7604 running with c7600s72033-advipservicesk9-mz.122-33.SRB3.bin. 7604 is running multilink bundling multiple E1's to other routers. We are running OSPF and MPLS over the multilink. The problem we are facing is if any one of the individual E1's reliability is going down we are observing the entire multilink's reliability is going down and the OSPF is stuck in EXSTART state. If we remove that problematic link from multilink everything is normal.

Would like to know this problem is related to any IOS bug in 7604. Also is there any configuration options that if the reliability of any E1's is exceeding a threshold we will exclude that link out of multilink and it will be included into multilink once the reliability is fine?

Thanks in advance.

Arun Kumar

I have this problem too.
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bagvanliju Wed, 10/29/2008 - 06:35


Kindly check the E1 (physical media get checked with BERT Meter from Service provider for this perticuler E1)....there are many reasons which reliablity can go down.most of the time it wud be a Physical layer issue.

Did u carried out end to end loop testing (Service provider can provide the loop from each node,so can identify which node is giving the problem )...

Pls let us knwo the status


arun kumar Wed, 10/29/2008 - 22:24


Yes i accept reliability issue relates to the physical layer. We carried out end to end physical loop testing and corrected it.

But my concern here is one link's reliability brings down the entire multilink's reliability and also OSPF is not coming up. Would like to know if this impact on multilink due to single E1 can be proactively avoided?


Arun Kumar

bagvanliju Thu, 10/30/2008 - 00:23


Thanks for the reply.U mean to say Reliablity of One E1 in multilink goes down that is effecting Reliablity of MultilinkXX. ?? ..if so that should not happen ..since its a virtual interface....did u try removing the multilink and configure it back ......

one more thing did u try removing the E1 which you suspect problem from multilink .....and see wheather OSPF is comming up or not ....


guruprasadr Thu, 10/30/2008 - 04:15

HI Arun Kumar, [Pls RATE if HELPS]]

The only option to Monitor the Multilink LINK Bundle is,

Configuring Multilink PPP Minimum Links Mandatory Example:

The following example shows how to configure a MLP bundle to be required to have at least five active sessions:

ppp multilink

multilink min-links 5 mandatory

Command Reference:


•multilink min-links

To specify the preferred minimum number of links in a Multilink PPP (MLP) bundle, use the multilink min-links command in interface configuration mode. To reset the default value, use the no form of this command.

multilink min-links links [mandatory]

no multilink min-links links [mandatory]

Hope I am Informative.


Best Regards,

Guru Prasad R


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