Question 500
An ISP migrates IPTV channels from ASM to SSM. Observed: Receiver packets still target a shared-tree RP that no longer has active mapping. What operational check best guards against this problem returning?
Explanation
Correct Answer
This control asks for the same recovery evidence (The (S,G) tree becomes active without RP dependency for SSM addresses) and flags recurrence of the same failure (Receiver packets still target a shared-tree RP that no longer has active mapping). It targets the underlying issue, legacy any-source join configuration remains after the ssm group move, rather than a different service problem. The exact cadence must be agreed with operations.
Incorrect Answers
The proposed control is tied to a control-plane filter blocks required pim packets on the transit segment, typically observed when pIM Hellos traverse a link whose multicast control traffic is filtered. Here the target is legacy any-source join configuration remains after the ssm group move; monitor the (S,G) tree becomes active without RP dependency for SSM addresses.
It is valid for another service scenario but checks sources transmit packets but receivers see none until a static join is added. This case instead needs a gate for receiver packets still target a shared-tree rp that no longer has active mapping and evidence that the (S,G) tree becomes active without RP dependency for SSM addresses.
This gate monitors a different failure, a legacy asm group is interpreted as source-specific and cannot use its rp. It would not detect the current problem: Receiver packets still target a shared-tree RP that no longer has active mapping. The appropriate check requires the (S,G) tree becomes active without RP dependency for SSM addresses.