Cisco Bug: CSCtc15675 - Packet stuck in PXF queue upon RF channel del/add for WB interface
Jan 31, 2017
- Cisco uBR10000 Series Universal Broadband Routers
Known Affected Releases
Symptom: If the last RF channel in a Wideband interface in DBS mode is removed and then a channel is added back to the same WB interface while there are untransmitted packets still sitting in any of the packet queues on that interface, the WB interface may be wedged, i.e., packets can no longer be transmitted on that WB interface. This trigger condition may happen when the channel removal and addition happen very rapidly under traffic through that WB interface (such as when changing rf-channel by pasting in a new configuration). It may also happen when the WB interface is being flow controlled or back throttled by OCQ, while the RF channel is unconfigured and then configured again inside the controller. To see if a packet queues on a WB interface are stuck, issue the command "show pxf cpu queue wideband 1/0/0:0" (substitute with the proper interface name) a few times. If the queue "Len" field is not zero, but the "Dequeues" count does not increase for any queue, that queue is stuck. In this case, further do "show pxf cpu stat queue | i Flowoff|OCQ" multiple times. If the flowoff and OCQ counters do not increase, it is a confirmation that the queues are stuck abnormally. In the example below QID 351397 is stuck full and is not dequeuing any packets. ubr10k#show pxf cpu queue wi1/0/0:5 Cable Interface Queues: QID Len/Max Dequeues TailDrops MinRt Wt/Quantum ShapeRt FlowId (Kbps) (Kbps) 131093 0/255 0 0 0 1/240 0 31 131094 0/255 0 0 0 1/10000 0 32797 Cable Service Flow Queues: * Best Effort Queues QID Len/Max Dequeues TailDrops MinRt Wt/Quantum ShapeRt FlowId (Kbps) (Kbps) 346016 0/255 0 0 0 1/240 10000 327573 343081 18/255 0 0 0 1/480 33000 102085 351397 255/255 0 348 0 1/480 33000 102086 351235 7/255 0 0 0 1/480 33000 102087 Conditions: This problem is seen in the field in two cases: 1) When there is rapid unconfiguration and then configuration of the RF channel frequency at the controller level, when those channels are actively transmitting packets. 2) When modifying the rf-channel configuration on a wideband bonding group quickly by pasting in configuration that adds and removes the channels while traffic is flowing.
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