Expected Behavior of Primary RE Failure | Juniper Networks Certified Internet Specialist

AC

When a Junos device has redundant RE's but no HA features enabled, and the master RE fails, the PFE restarts and all hardware and interfaces are discovered by the new master RE. The new master RE starts rpd so that all adjacencies are aware fo the topological changes.

In a Junos device with dual Routing Engine (RE), the primary and backup REs work together as a team to provide high availability (HA) for the device. The primary RE is responsible for processing control plane traffic and managing the routing protocols, while the backup RE is on standby, ready to take over if the primary RE fails.

When the primary RE fails, the backup RE must assume the role of the primary RE to maintain the device's operation. Here are the expected behaviors when the primary RE fails:

B. The backup RE will immediately assume the master role Once the primary RE fails, the backup RE immediately takes over as the new master RE, assuming control of the routing protocols and other control plane functions. The backup RE continues to use the same IP addresses and hostnames as the primary RE, so the network topology and management remain unchanged.

C. The new master RE restarts the routing protocol process (rpd) and establishes any required adjacencies based on the configuration. When the backup RE takes over as the new master RE, it needs to restart the routing protocol process (rpd) to establish the protocol adjacencies based on the configuration. This ensures that the routing information is up-to-date and that the network continues to function correctly.

A. The backup RE will assume the master role once the packet forwarding engine (PFE) restarts This statement is not entirely accurate. The backup RE assumes the master role as soon as the primary RE fails, regardless of whether the PFE restarts or not. However, once the new master RE takes over, it may need to synchronize with the PFE to ensure that the forwarding plane is also operating correctly.

D. The new master RE maintains the existing protocol adjacencies initially established by the previous master RE This statement is not entirely accurate. When the new master RE takes over, it needs to establish new protocol adjacencies based on the configuration. While some of the adjacencies may be maintained, it is not guaranteed that all of them will remain active.

In summary, the expected behaviors when the primary RE fails are that the backup RE immediately assumes the master role, the new master RE restarts the routing protocol process (rpd) to establish new protocol adjacencies based on the configuration, and it may need to synchronize with the PFE to ensure that the forwarding plane is also operating correctly.