Exam JN0-348 topic 1 question 18 discussion

Most graceful restart implementations define two types of routers—the restarting router and the helper router. The restarting router requires rapid restoration of forwarding state information so it can resume the forwarding of network traffic. The helper router assists the restarting router in this process. https://www.juniper.net/documentation/us/en/software/junos/high-availability/topics/topic-map/graceful-restart-understanding.html

AC correct

The primary drawback to GR is the need for protocol extensions and helper support in neighboring routers, and a stable network topology. If any neighbors do not support GR, or if other changes occur in the network, GR ends up aborting and loss results in the dataplane. Even when all goes to plan and the GR event succeeds, which means there is zero loss in the data plane, there is still control plane flap and a subsequent need for protocol reconvergence between the restarting router and its helpers, ... The correct answer are : A, C

It is a bit confusing, GRES will still work without GRES extensions and helper routers, but RPD will need to restart and it will be like booting a router from scratch, it will take time to get the routing process up. Helper routers reduce the time by passing along routing info

ref.: https://www.oreilly.com/library/view/juniper-mx-series/9781449358143/ch09s03.html