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[MX] New RE has a different chassis network-services mode than primary RE

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Article ID: KB32167 KB Last Updated: 28 Jun 2021Version: 2.0
Summary:

After changing the backup Routing-Engine (RE), the new RE might have a different chassis network-services mode than the primary RE. The issue can be discovered only when a primary role switch occurs after graceful Routing Engine switchover (GRES) to the new installed RE.

This article recommends performing a reboot after installing the new RE and the required Junos OS software to ensure that new values are incorporated and validated.

Cause:

The issue can be explained with the following sequence of events:

  1. After RE0 failure, RE0 is replaced.

  2. The new RE might have a different Junos OS version and some default configuration such as "chassis network-services" is "IP." 

  3. Because the version of Junos OS on RE0 differs from the one on RE1, the configuration is not synchronized. Otherwise, the GRES configuration would force a configuration synchronization. So the value of "chassis network-services" is not applied to the RE0 (for example "enhanced-ip").

  4. Junos OS is upgraded on RE0.

  5. When RE0 is online after software installation, the configuration from RE1 (with "chassis network-services enhanced-ip" configured) is applied due to GRES configuration and a commit synchronizes the configuration. However, the new RE0 is not rebooted with the new network-services configuration and no explicit warning is generated about the requirement of rebooting RE0 for the new value of network-services to take effect.

  6. After GRES switchover to RE0 and post-configuration changes with a commit, warning messages are displayed that a reboot is required. The GRES switchover to RE0 can happen several months after the RE replacement, so it might be difficult to identify the reason for the warning messages. Moreover, the output of show chassis network-services shows only the configured value but not the programmed value:

lab@router-re0# commit
warning: graceful-switchover is enabled, commit synchronize should be used
[edit]
  'chassis'
    warning: Chassis configuration for network services has been changed. A system reboot is mandatory.  Please reboot *ALL* routing engines NOW. Continuing without a reboot might result in unexpected system behavior.
commit complete

[MASTER]
lab@router_re0> show chassis network-services
Sep 08 09:48:51
Network Services Mode: Enhanced-IP
 
[MASTER]
lab@router_re0> show configuration chassis network-services
Sep 08 09:48:56
network-services enhanced-ip;

However, the actual programmed value can be seen from shell:

[MASTER]
lab@router_re0> start shell
Sep 08 09:49:36
% sysctl -a | grep netsvc
‚Äčnet.netsvc: 0

The value of the net.netsvc variables are:

  • 0 : IP

  • 1 : ethernet

  • 2 : enhanced IP

  • 3 : enhanced Ethernet

  • 4 : all IP

  • 5 : all Ethernet

  • 6 : enhanced mode

  • 7 : lan

Solution:

After installing the new RE and the required Junos OS software, perform a reboot. It is important to validate the network-service programmed value with the following shell command:

[MASTER]
lab@router_re0> start shell
Sep 08 09:49:36
% sysctl -a | grep netsvc
net.netsvc: 0

If the programmed value differs from what is configured, a system reboot of the new RE is required.

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