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Cisco Bug: CSCun15817 - Umbrella DDTS for PVRST on 5.1.1

Last Modified

Jul 20, 2018

Products (7)

  • Cisco ASR 9000 Series Aggregation Services Routers
  • Cisco IOS XR Software
  • Cisco ASR 9922 Router
  • Cisco ASR 9010 Router
  • Cisco ASR 9006 Router
  • Cisco ASR 9001 Router
  • Cisco ASR 9912 Router

Known Affected Releases


Description (partial)


On PVRST to MST config rollback it is observed that bundle interface for  instance 0 is stuck in DSG BLK state even for the root bridge. However instance 1 bundle interfaces are in correct DSG FW state. 

pvstag-io process abnormally terminates. If the protected port is a bundle interface, the standby process will continuously restart, outputting error messages about checkpoint data not being found.

stp_controller process abnormally terminates when configuration is rolled back from PVRST to MSTP. The process restarts without no other impact.


The issue is of the MST instance 0 interfaces getting stuck is seen on IOS-XR 5.1.0 when PVRST to MST config rollback is performed. 

Configure PVRST on a port which also includes VLANs which are not protected by PVRST. Remove the PVRST port configuration. Subsequent attempts to configure PVRST on the port & VLAN which was not previously protected will trigger the issue.

A system is booted with PVRST configuration or is configured for PVRST then the stp_controller process is restarted. This sets up the inconsistent internal state which then triggers the abnormal termination when PVRST config is removed and MSTP is configured.
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