[c-nsp] IMA Interface/PVC flapping issue

[Mark Rogaski]

An entity claiming to be Michael Nicks (mtnicks at kanren.net) wrote:
: I've had this PVC rebuilt probably 10 times already. I've had other PVCs 
: on other equipment also rebuilt many times, to no avail. Regular ATM T1s 
: terminated on the same physical path within the telco's network are not 
: exhibiting these symptoms. Also this is not isolated to just one telco 
: vendor, it's happening with every telco vendor that has provisioned IMA 
: service for us.
: 

Rarely does a PVC-level event impact port-level operation.  I suspect that
the order of the log entries is just a minor timing issue with the
logging.  I doubt that rebuilding the PVC will have any impact.  The 
symptoms you are reporting match what you would expect with a timing issue.
Here are some things to check.

  sh controller t1 0/0
  sh controller t1 0/1

Make sure that you have line timing configured.  Look for slips or frame
loss.

  sh network-clocks

Verify that one of the T1's is being used as a reference.

  sh ima int atm 0/ima0 detail

Verify that the clock mode is CTC.  Look for errors under group and link
counters.

If your ticket with AT&T is being handled by the FR/ATM NOC or by Tier 3/4,
you can ask to have them look at the following commands on the AUSM or MPSM
card that the port is configured on.

  dspimainfo
  dspimalncnt
  dspimagrpcnt

Also, it might be worth dropping all but one line on an IMA group to see if
you have the problem with a single-link IMA group.  If you don't and you
don't see evidence of timing slips on the T1, that would isolate the issue 
to the IMA layer.

Mark

-- 
[]                      |
[] Mark Rogaski         |    Nothing spells caveat emptor like a mannequin
[] wendigo at pobox.com    |    with a severed head.
[] mrogaski at cpan.org    |    -- Brooke McEldowney, _9 Chickweed Lane_
[]                      |
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