問題文
Three domains are joined by MSDP. The third rendezvous point peers with both of the others, and its unicast path back toward the first one runs through the second. On the third one the counter of rejected messages climbs for a source that sits in the first domain, while both peerings stay up and the source is a real one that is still sending. What accounts for the rejected count?
選択肢
- The check that runs here is the same reverse path check that a device runs on the data of a group, so the count tracks the state of the route toward the source rather than the route toward the rendezvous point that raised it.
- The counter is raised for a message whose source is already known inside the local domain, so what it reports is a duplicate rather than a message that was dropped.
- A message of this kind is taken from the peer that lies along the path back toward the rendezvous point that raised it, and the rest are dropped and counted, which is what holds these messages back from looping.
- A message of this kind is taken from a peer whose own domain holds the source that the message names, so a message that has already crossed one domain on its way toward the third rendezvous point is dropped and counted.