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Cisco Bug: CSCuj58299 - CUBE Input queue wedge RTCP packets - 180w/o SDP followed by 180w/SDP

Last Modified

Apr 24, 2020

Products (1)

  • Cisco IOS

Known Affected Releases


Description (partial)

Interface input queue starts to become congested.  The input queue can reach the input queue maximum which will cause problems for all control-plane and punted traffic (management, routing protocols, call control, etc).  

Example from "show interface" output:

Input queue: 76/75/0/5549 (size/max/drops/flushes); Total output drops: 0

It may seem like the router becomes "unresponsive" and may require a reboot to restore service.  Access from the console will still be possible.  After some time, the input queue can clear on it's own.

This symptom is observed under the following conditions:
1) Router serves as a SIP-SIP CUBE
2) Packets that are congesting input queue are RTCP packets.  Check  "show buffers input-interface [interface] packet". (RTCP packets are most commonly odd source/destination UDP ports in the range 16384 - 32768)
3) CUBE receives a 180 without SDP followed by a 180 with SDP on one of the call legs (collect 'debug ccsip message' for a period of time leading up to and including when you see the input queue begin to fill)
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