Refer to attachment firstly.
1. Customer A try PING to customer B, but some packets loss.
2. Customer A try PING to customer C, also some packets loss.
3. Cut the RPR link between NE40-3 and NE40-2, RPR swap. Customer A try PING to customer B again, now no packet loss.
PING packet lost.
We check the loss packet on RPR board with some diagnosis command, but we cannot find any loss.
1. We made a plan to change RPR boards. Firstly change side B board of NE40-3, if the PING test still not smooth after changing, we continue to change side A board of NE40-2.
2. After changing side B board of NE40-3, we test PING service, all is OK. We can make the conclusion the side A RPR board of NE40-2 is wrong.
1. The packet forwarding path is below.
Packets flow from NE40-3 to NE40-2:
NE40-3 (side A) to NE40-3 (mate cable) to NE40-3 (side B) to NE40-2 (side A)
Packets flow from NE40-3 to NE40-4:
NE40-3 (side A) to NE40-3 (mate cable) to NE40-3 (side B) to NE40-4 (side A)
Just from this path, we cannot judge which board is failed. It seems that any board here is possible to get wrong.
2. But if we cut the RPR link between NE40-3 and NE40-2, RPR ring will swap at side A of NE40-3. the PING packet should go this way, NE40-3 (side A) to NE40-4 to NE40-1 to NE40-2 (side B), and the PING is smooth.
3. So we can exclude the problem of side A board of NE40-3 and side B board of NE40-2. The problem should be caused by side B board of NE40-3 or side A board of NE40-2, but we cannot confirm which one is really wrong. We need to change the boards one by one.
Get to know the packets forwarding flow on RPR ring, you can handle similiar problems easier. The arrow lines in attachment indicate the packets forwarding flow on RPR ring.