Description

This article describes the issue of  'request system reboot <all-chassis> ' on the SFC backup causing traffic to be disrupted, when the Re mastership is inconsistent.

Symptoms

In normal conditions, the RE mastership is consistent on SFC and LCC. the Junos upgrade can be implemented via the following procedure:

  1. Logon to the Primary Routing Engine on the TX Matrix Plus router.

  • Disable Routing Engine Redundancy and GRES on the Routing Matrix.

  • Install Junos OS on the backup Routing Engines.

  • Load the software on the backup Routing Engines.

  • Switch the Routing Engine Mastership to the backup Routing Engines.

  • Install the software on the new default Primary Routing Engines.

  • Load the software on the new default Primary Routing Engines.

  • Switch the Routing Engine Mastership back to the default Primary Routing Engines (optional).

  • Restore the original configuration.

  • Back up the Routing Engines.

When the RE mastership is not consistent between SFC and LCC (SFC-RE0 and LCC$-RE1 are Primary REs), step 4 and step 7 will break the connection between SFC-Primary and LCC-Primary and cause traffic to be disrupted.

Solution

For multi-chassis TXP to operate without any traffic loss, it is absolutely necessary to keep the path, from SFC-Primary to LCC-Primary, up all the time. When SFC-RE0 and LCC-RE1 are the masters, there are two redundant paths between them:

  • SFC-RE0 <--igbe1--> SFC-CB1 <----> SFC-CIP1 <----> LCC-CB1 <--bcm0--> LCC-RE1

  • SFC-RE0 <--igbe0--> SFC-CB0 <----> SFC-CIP0 <----> LCC-CB0 <--em1--> LCC-RE1

When SFC-RE1 is rebooted, path 1 is broken as SFC-CB1 and SFC-CIP1 are reset. When LCC-RE0 is rebooted, path 2 is broken as LCC-CB0 is reset. When request system reboot <all-chassis> is issued on SFC-RE1, both SFC-RE1 and LCC-RE0 are reset, both paths are broken, and SFC-RE0 cannot communicate with LCC-RE1.

Workaround:

  1. Reboot the SFC backup by using request system reboot sfc x .

  • Wait until the SFC backup fully boots up and ensure that show chassis routing-engine on the SFC-Primary shows it as online.

  • Now reboot all LCC backup's by using request system reboot all-lcc on the SFC backup.

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