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Cisco 3925 T1 Issues

William Scott


I'm reaching out because I am out of ideas on this particular issue that I have been working over the last two months.  We have a site that has 2xT1 service from AT&T which is in a PPP Multilink bundle.  Basically the issue is when the 1st circuit is in the multilink bundle the router becomes extremely sluggish and it will kick you out of the router.  Currently there are no errors on the interface (either one).  We are using the VWIC2-2MFT-T1/E1 which is NOT set to independent clocking.  We use the following:  channel-group 0 timeslots 1-24.

We have had the extended wiring replaced (all brand new), we have RMA'd the WIC card in the router (same issue occurs), AT&T tests the circuit clean repeatedly, we have even done head to head testing on site, and AT&T has found no issue.  Just wondering if anyone else has ever ran into this issue and what their fix action might have been.  I'm out of ideas.  Thanks in advance for reading this.



It looks as if your layer 1 is fine, but you may need to look at layer 2.  I would start looking at the layer 2 interface (I'm guess PPP), and see if you are logging any input errors.  I've seen numerous situations where the DSLAM on the provider side had a bad card.  T1's were clean, but the card would spit out garbage when it came to PPP from time to time.  The provider ended up having to move us to a different card on each instance.

Cool.  Appreciate the insight.  I am working with the provider now trying to see what the heck is on going on.  Not seeing any input errors, typically both circuits run clean.  One interesting thing I am finding is that the provider is seeing where the PE is not sending us outbound traffic from the PE side.  Unsure yet if it's due to L1/L2 issue or if it's a configuration issue.  Will report back on this thread once we figure it out in the event someone else ever runs into this in the future.

If that is the case, it may be helpful to configure a traffic-export on the interface to get a packet capture off of the T1 interface.  WIth that you could confirm what traffic is and isn't hitting your router.

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