Technical data

Known limitations and considerations in this release 53
Release Notes for the Passport 8600 Release 3.7.6
The source->upstream on R1 becomes NULL, because it is getting data
locally through 1/2. When R2 comes back up, traffic starts flowing on 1/1 to
R2. However, if the unicast route to the source subnet still lies through R1
(since R2 rebooted), any joins to the source go to R1 instead of R2. To receive
traffic, R1 must send a join to R2, but because the source->upstream is NULL
the join is never sent.
To avoid this issue, always connect the lowest IP address (non-DR) to the
lowest MLT port on the BPS. For example, in the above diagram, 1/1 should
go to R1. Always use FWD_TO_DR on R1 so that both R1 and R2 will
receive traffic. In this case, whichever switch receives the join after a reboot
can receive and forward traffic. (Q00658544)