[c-nsp] Sup2T 15.1(SY1) inline packet traffic crash

Charles Spurgeon c.spurgeon at austin.utexas.edu
Wed Feb 5 15:23:58 EST 2014

FYI. We recently encountered an inline packet crash bug that took out
two Cat 6509 routers, each equipped with two Sup2T supervisors. All
sups crashed within seconds of one another.

In other words, both routers in a dual resilient router design, with
dual sups in each of the routers, crashed and reloaded when all sups
crashed within the same minute. This caused an outage while both
routers reloaded.

The routers operate independently with no VSS config. We did not
change the MTU on any interface or any other part of the config, and
the crash occurred at midnight with no one logged into the devices.

Cisco TAC cited this bugID: CSCuf60783, which has a Severity 2, states
that VSS is involved, implies that an MTU config is involved, and
describes the chance of hitting the bug as low. Needless to say, we
don't agree with any of those assertions.

We were told that inline packets transiting the data plane caused the
crash. Luckily there was not a repeat of the packet traffic that
triggered the bug, so after the crash both boxes came back up and
continued to function.

TAC advised a reload on 15.1(2)SY1, which we have done.


Charles E. Spurgeon
University of Texas at Austin / ITS Networking
c.spurgeon at its.utexas.edu / 512.475.9265

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