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300-415 · Question #223

300-415 Question #223: Real Exam Question with Answer & Explanation

The correct answer is A: omp no shutdown graceful-restart timers holdtime 120. To ensure WAN Edge routing tables are refreshed within 2 minutes after a vSmart connection is restored, the OMP graceful-restart holdtime must be configured to 120 seconds. This specifies how long a WAN Edge will retain routes learned from a vSmart during a temporary control plan

WAN Edge Router Deployment

Question

A company deploys a Cisco SD-WAN solution but has an unstable Internet connection. When the link to vSmart comes back up, the WAN Edge router routing table is not refreshed, and some traffic to the destination network is dropped. The headquarters is the hub site, and it continuously adds new sites to the SD-WAN network. An engineer must configure route refresh between WAN Edge and vSmart within 2 minutes. Which configuration meets this requirement?

Options

  • Aomp no shutdown graceful-restart timers holdtime 120
  • Bomp no shutdown graceful-restart timers advertisement-interval 120
  • Comp no shutdown no graceful-restart
  • Domp no shutdown graceful-restart timers eor-timer 120

Explanation

To ensure WAN Edge routing tables are refreshed within 2 minutes after a vSmart connection is restored, the OMP graceful-restart holdtime must be configured to 120 seconds. This specifies how long a WAN Edge will retain routes learned from a vSmart during a temporary control plane outage.

Common mistakes.

  • B. The 'advertisement-interval' timer controls how often OMP updates are sent, not how long routes are held during a graceful restart scenario.
  • C. Disabling graceful restart ('no graceful-restart') would cause routes to be flushed immediately upon vSmart adjacency loss, exacerbating the problem of dropped traffic during unstable connections, not solving it.
  • D. The 'eor-timer' (End-of-Rib timer) is related to the time a router waits to receive all routes from a peer after establishing an adjacency, not for holding routes during an outage.

Concept tested. OMP Graceful Restart Hold Time

Reference. https://www.cisco.com/c/en/us/td/docs/routers/sdwan/configuration/sdwan-xe-gs-book/sdwan-routing.html#concept_x3t_j2j_vnb

Topics

#SD-WAN OMP#Graceful Restart#Route Refresh#WAN Edge Configuration

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