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[MX] GRES switchover status is 'not ready' when routing-engine DRAM are mismatched in size

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Article ID: KB34869 KB Last Updated: 03 Apr 2021Version: 2.0
Summary:

This article discusses a scenario where the GRES switchover status appears in 'not ready' state when DRAM mismatch is found in routing-engine for MX2000 platforms. The switchover still works as expected, but RMA may be required to resolve the issue.

Symptoms:

Running 15.1F5 code before upgrading:

root> show chassis routing-engine | match dram
DRAM                      16334 MB (16384 MB installed)
DRAM                      32718 MB (32768 MB installed)

[MASTER]
root> request routing-engine login other-routing-engine

--- JUNOS 15.1F5-S4.6 Kernel 64-bit JNPR-10.1-20160724.331042_builder_stable_10
[BACKUP]
root> show system switchover
Graceful switchover: On
Configuration database: Ready
Kernel database: Ready
Switchover Ready <-- Note the switchover status as 'ready'

After upgraded to 17.4R2 Code:

show chassis routing-engine | match dram
DRAM                      16334 MB (16384 MB installed)
DRAM                      32718 MB (32768 MB installed)

root> show system switchover
Jun 27 18:24:18
Graceful switchover: On
Configuration database: Ready
Kernel database: Ready
Switchover Status: Not Ready <-- Note the status changed to 'not ready' 
Cause:

Due to a new software feature introduced in Junos 17.1, certain process changes were done for replicating session database to the backup RE when GRES is enabled. For this feature to work, all the routing-engines in the system must have the same size of DRAM. In this case, due to memory mismatch, GRES is in 'Not Ready' state on the backup RE after the upgrade.

Solution:

Contact your JTAC representative for an RMA to replace the routing-engine to match the DRAM size of both the primary and backup REs on the same system. (See Symptoms field above for command to check the size.)

Even though the switchover status shows 'not ready', the switchover works as expected.

A problem report (PR) has been created to raise an alarm (which is addressed in 17.4R3 and later releases), if there is a DRAM size mismatch in the system.

Modification History:
2021-03-25: Updated the article terminology to align with Juniper's Inclusion & Diversity initiatives
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