300-415 · Question #335
How do WAN Edge devices operate when vSmart is inaccessible or fails to be reached by the WAN Edge?
The correct answer is B. They continue operating normally for a configurable time. WAN Edge devices continue to operate normally for a configurable period, forwarding data plane traffic based on their last known policies, even if the vSmart controller becomes inaccessible.
Question
Options
- AThey continue operation normally.
- BThey continue operating normally for a configurable time.
- CThey continue to receive reachability updates.
- DThey cease to forward traffic in the data plane.
How the community answered
(31 responses)- A3% (1)
- B90% (28)
- C6% (2)
Why each option
WAN Edge devices continue to operate normally for a configurable period, forwarding data plane traffic based on their last known policies, even if the vSmart controller becomes inaccessible.
They do not continue 'normally' indefinitely; there is a time limit before operations are impacted, specifically if new policy or routing updates are required.
When a WAN Edge device loses connectivity to vSmart, it retains its last received policies and routing information and continues to forward data plane traffic based on those policies for a configurable 'dead-peer-detection' (DPD) or 'control-connection-timeout' interval.
WAN Edge devices cannot receive reachability updates from vSmart if vSmart is inaccessible.
WAN Edge devices do not immediately cease forwarding data plane traffic; they maintain their current state and forward traffic for a grace period.
Concept tested: Cisco SD-WAN vSmart controller failure impact
Source: https://www.cisco.com/c/en/us/td/docs/routers/sdwan/configuration/sdwan-xe-17-book/sdwan-system-config.html
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