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3 ISP link issue

smitesh kharecha

Hi All,

Witnessing a strange issue in our setup.

I will try to sum up everything as below:

* We have 3 ASR ( ISP Managed) on which we had terminated 3 ISP MPLS links.

* 6500 is connected with those 3 ASR.

* Out of those 3 links, 2 are in production in load sharing mode ( BGP multilink)

* No problem or even no intermittent problem witness as long as we run on 2 ISP links

* As soon as we introduce 3rd link, we start getting all sort of problem with Voice call issues to ghost call to one way voice, etc.

* Voice is already market with EF on IP Phone and is honoured and put in priority queue on 6500

* No drops observed to ASRs or even remote edge sites.

* No collision, CRC or any other errors witnessed.

* ISP says no problem observered at their end.

I have now run out of ideas to troubleshoot the issue. I definate think issue should be be with that particular 3rd ISP link; however ISP says to provide them proof for further action.

Any directional or conceptual help highly appriciated.

PS: Due to NDA, I won't be able to provide any command outputs, however I can check anything particular you need and give you feedback.


Smitesh Kharecha

Message was edited by: smitesh kharecha

4 Replies 4

Jon Marshall
VIP Community Legend VIP Community Legend
VIP Community Legend


The only thing i can think of is the that the third ISP is not honouring your markings correctly.

I am assuming that with your existing ISPs you have QOS provided by them within the MPLS cloud ?

So even though you may not be seeing any drops at the remote end that does not mean they are being delivered within the time contraints required by VOIP.


Thanks Jon,

I had already checked by making basic ACL matching packets for EF and tried end to end extended ping, which were succesfull.

I confirm EF is honoured in telco cloud.

What else can be the reason.




I doubt this could be the problem as you are already running ovet two separate ISP links but i was wondering about packets arriving out of order because you have multiple links. Out of order packets can significantly affect voice packets so i wonder if this could be an issue.

Like i say, unlikely, but just suggesting possible causes.



Just a clarification, all 3 links are from same ISP.

As far as your doubts goes over packet arriving out of order, even I doubted the same, however I'm still wondering how to check that and what action as such can be taken to rectify out of order packet arrival issue.



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