Network services modes provide inter-operability with different kinds of modules within the chassis. For a list of available modes, refer to Network Services Mode Overview .
In a router configured with graceful-switchover, changing the network services mode requires a reboot of the whole router to propagate the network-service mode to the RE's kernel and FPCs. A new RE usually comes with factory-default configuration having network-service mode set to IP (the default mode). Many customers use enhanced-ip/enhanced-ethernet network-service mode in MX routers. Operators usually do not expect to reboot the whole router to replace an RE in a system enabled with graceful-switchover. If an RE replacement is not carefully executed on an MX router enabled with graceful-switchover and network-service mode set to any mode other than 'IP', the router may end up in a state where there is a mismatch in network-service mode setting in the kernels of both REs and FPCs. Once this occurs, a reboot of the whole router is required to make the network-service mode consistent across the kernel of both REs and FPCs, otherwise the router behavior can be unpredictable. Rebooting the whole router may not be a desirable step for most operators installing a new RE in a router enabled with graceful-switchover. This article provides recommendations for performing RE replacement on an MX router configured with graceful-switchover and network-services mode set to enhanced-ip/enhanced-ethernet.
RE replacement on an MX configured with graceful-switchover and 'network-services enhanced-ip/enhanced-ethernet' should follow the sequence of events described below:
Ensure the RE to be replaced is the backup RE.
Disable graceful-switchover (and NSR, if applicable) on the primary RE and commit the configuration.
Power down the backup RE (the RE to be replaced) using 'request system halt other-routing-engine' from the primary RE.
'request system halt other-routing-engine'
Remove the backup RE and insert the new RE.
Once the new RE is powered on, make sure the Junos version in the new RE is the same as the primary RE. If not, install the required image on the new RE.
After step 5, once the new RE is online with the required Junos version, perform commit synchronize from the primary RE. This will change the network-service mode in the new RE from IP (default) to the one set in the primary RE's configuration.
Reboot the new RE to propagate the network-service mode configuration change to the new RE's kernel.
Once the new RE is online after step 7, enable graceful-switchover (and NSR, if applicable) on the primary RE and commit the configuration.
Once the new RE is ready to be the primary, mastership can be switched if desired.
If the steps above are not followed in the order mentioned, then the router may end up in a state of network-services mode inconsistency as documented in KB31920 - Routers with dual routing engines assert an inconsistent state [juniper.net] . You can also refer to KB31920 [juniper.net] for the commands to verify the network-services mode in the system.
2020-07-24: Fixed broken link.