This article explains if there is any effect on protocol adjacencies when the graceful restart configuration is deleted and the non-stop routing configuration is applied in the same commit operation.

Graceful Restart (GR) and non-stop routing (NSR) are two different mechanisms that provide high availability on Juniper platforms.

Non-stop routing is applicable on systems with dual Routing Engines and when a Routing Engine goes down. Graceful Restart, on the other hand, deals with the entire router restarting and the related protocol convergence remaining hidden from the rest of the network with the assistance of a helper router.

Both are mutually exclusive and cannot be configured together on a device, which leads to the following questions:

• Can we enable NSR and remove GR on the device in the same commit?
• Will the commit go through?
• Is there any impact on protocol adjacencies if the configuration change goes through?

If NSR with GR in place is applied, the commit will be rejected. However, in the same commit, you can disable GR and enable NSR.

Example: 

delete routing-options graceful-restart
set routing-options nonstop-routing
commit

Note: This change may cause existing protocol adjacencies to flap. For example, all BGP sessions will flap. Therefore, ensure that you make these changes during a planned Maintenance Window.

Further, the high availability mechanism that you would like to configure on the device will depend on the platform (if it supports and has dual RE or not) and what you want to achieve from the configuration.

2021-04-01: Added a note in the Solution section about existing protocol adjacencies flapping during the said change