Which two conditions occur when the primary route processor fails on a switch that is using dual route processors with stateful switchover? (Choose two.)
A.
Data forwarding can continue along known paths until routing protocol information is restored.
B.
Data forwarding is stopped until the routing protocols reconverge after the switchover.
C.
The standby route processor is fully initialized and state information is maintained.
D.
User sessions are immediately recreated on the new active route processor.
E.
The standby route processor initialization is started when the primary router processor fails.
A and C
from the 2nd edition OCG under SSO and NFS section, "During a switchover, the standby RP takes over as the new active RP. The new active RP uses the SSO learnt checkpoint information and keeps the interfaces on the router from flapping and the router and/or line cards from reloading, however, SSO doesn’t checkpoint any Layer 3 control plane information about any neighbor router, and due to this, the existing routing protocol adjacencies go down and begin to reestablish. During this time, since the FIB was checkpointed by NSF, the data plane is not affected by the Layer 3 control plane going down and traffic continues to be forwarded while the routing protocol adjacencies reestablish. After routing convergence is complete, the FIB is updated with new routing or topology information from the RIB if necessary."
also it states "SSO/NSF is not a configurable feature; it is enabled by default when SSO is enabled, this means that any NSF command or keyword found in the documentation or the command line, is referring to Graceful Restart." meaning when you enable SSO you also enable NSF is what it seems. so I go with AC
SSO ensures the standby RP is fully synchronized and initialized before it takes over (confirms option C).
When the primary RP fails, the standby RP immediately takes over control.
However, without NSF enabled, data forwarding is disrupted during the switchover because line cards lose route processor control temporarily.
This means routing protocols must reconverge, and data forwarding pauses (supports option B).
NSF (Nonstop Forwarding) is a separate feature that must be explicitly enabled to maintain data forwarding without interruption during switchover.
BC - No mention of NSF in place here, which is not enabled by default and requires explicit configuration.
If NSF was enabled the answer would be AC, without NSF the answer is BC
During a switchover, the standby RP immediately
takes control and prevents basic problems such as
interface link flaps. However, Layer 3 packet forwarding
is disrupted without additional configuration. The RP
switchover triggers a routing protocol adjacency flap that
clears the route table. When the routing table is cleared,
the CEF entries are purged, and traffic is no longer
routed until the network topology is relearned and the
forwarding table is reprogrammed. Enabling nonstop
forwarding (NSF) or nonstop routing (NSR) high
availability capabilities informs the router(s) to maintain
the CEF entries for a short duration and continue
forwarding packets through an RP failure until the
control plane recovers.
BC - No mention of NSF in place here, which is not enabled by default and requires explicit configuration.
If NSF was enabled the answer would be AC, without NSF the answer is BC. Hmm
SSO-enabled routers
always checkpoint line card operation and Layer 2 protocol states. During a switchover, the
standby RP immediately takes control and prevents basic problems such as interface link
flaps. However, Layer 3 packet forwarding is disrupted without additional configuration (without NSF).
I am doubting the answer should be AC or BC...
A requires NSF which cannot be simply done with SSO. Without NSF the CEF entries are purged and routing table is cleared. Routing protocols need time to relearn and rebuild routing table on the standby processor, which B seems describing more precisely.
E is not correct because processor initialization is done when activating SSO, the bulk synchronization initializes standby processor. After SSO startup completes there will be only regular checkpoints to perform increment synchronization to standby processor.
Any thought?
C is correct because the standby route processor is fully initialized and maintains the state information of the system. This ensures that there is no loss of state information during the switchover process, and the system continues to function normally without interruption.
E is correct because the initialization of the standby route processor begins as soon as the primary route processor fails. This ensures that the standby route processor is fully operational and can take over the duties of the primary route processor seamlessly.
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