352-001 · Question #29
Refer to the exhibit. How would you adjust the design to improve convergence on the network?
The correct answer is A. Add an intra-POP link between routers 1A and 1B, and enable IP LFA FRR.. Adding an intra-POP link between 1A and 1B combined with IP LFA FRR enables pre-computed alternate paths for sub-second failover, directly improving network convergence.
Question
Refer to the exhibit. How would you adjust the design to improve convergence on the network?
Exhibit
Options
- AAdd an intra-POP link between routers 1A and 1B, and enable IP LFA FRR.
- BUse an IP SLA between the end stations to detect path failures.
- CEnable SSO-NSF on routers 1A and 1B.
- DUse BGP to connect the sites over the WAN.
How the community answered
(14 responses)- A64% (9)
- B7% (1)
- C7% (1)
- D21% (3)
Why each option
Adding an intra-POP link between 1A and 1B combined with IP LFA FRR enables pre-computed alternate paths for sub-second failover, directly improving network convergence.
An intra-POP link between 1A and 1B creates the topology redundancy required for IP Loop-Free Alternate (LFA) Fast ReRoute (FRR) to operate. LFA FRR pre-computes alternate next-hops during normal operation so that upon a link failure, traffic is immediately redirected without waiting for the IGP to reconverge. This combination of physical redundancy and pre-computed alternate paths is the most direct method to improve convergence speed in the described design.
IP SLA monitors path conditions and can trigger route changes, but it detects failures reactively rather than providing pre-computed alternate paths, so it does not meaningfully improve convergence speed.
SSO-NSF (Stateful Switchover with Non-Stop Forwarding) preserves forwarding state during a control-plane restart on a single device but does not address topology convergence for link or node failures.
BGP is inherently slow to converge compared to IGP-level mechanisms like LFA FRR, and routing the WAN with BGP alone would not improve convergence time within the POP.
Concept tested: IP LFA FRR for sub-second convergence
Source: https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/iproute_ospf/configuration/xe-16/iro-xe-16-book/iro-lfa-frr.html
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