What are two ways that nonstop routing works? (Choose two.)
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A. B. C. D.AD
Nonstop routing is a feature in Junos OS that allows the control plane of a router to continue forwarding traffic even if the primary Routing Engine (RE) fails. Nonstop routing works by maintaining redundant Routing Engines and enabling them to quickly take over the control plane functions in the event of a primary RE failure.
There are two ways that nonstop routing can work:
A. By enabling redundant REs to switch from primary RE to backup RE: In this method, the primary and backup Routing Engines are continuously synchronized. When the primary RE fails, the backup RE takes over as the active control plane, and the forwarding plane continues to forward traffic. The process of switching from the primary RE to the backup RE is automatic and transparent to the network.
C. By enabling redundant REs to run a different version of the Junos OS: In this method, the primary and backup Routing Engines run different versions of the Junos OS, but both maintain a synchronized copy of the routing table. When the primary RE fails, the backup RE takes over and continues to use the synchronized routing table to forward traffic. This method allows for non-disruptive software upgrades, as the backup RE can be upgraded while the primary RE continues to handle traffic.
Option B, "by alerting peer nodes of any routing table changes," is not a correct way that nonstop routing works. While nonstop routing does ensure that the routing table is continuously synchronized between primary and backup REs, it does not rely on alerting peer nodes of any routing table changes.
Option D, "by replicating routing protocol information," is also not a correct way that nonstop routing works. While nonstop routing does maintain a synchronized copy of the routing table, it does not rely on replicating routing protocol information to maintain this synchronization.