I have a single "remote" SRX setup with a pair of GRE/IPSec tunnels, each to a different "hub" SRX gateways (ie 3 SRX boxes in total in this setup). I'm using GRE so I can send multicast traffic from the remote to both hubs. So, oddly, I can send multicast traffic in one direction over both tunnels, but ping does not work on just one of those tunnels. The other one is working fine. From what I can tell, everything is configured identically between the two tunnels on both ends.
On the single SRX with 2 tunnels, I am using gr-0/0/0.0 and gr-0/0/0.1 interfaces. I even tried swapping the tunnels between the two interface units to see if that would help, but it didn't. I haven't switched the underlying ge or st ports because I don't think that should matter.
From what I can see, the routing table is not being updated for the second tunnel on the remote, even after I switch the gr interface units used. The tunnel does show as UP, but cannot ping across it.
I also tried using gr-0/0/1.0 instead of gr-0/0/0.1 -- then the gre tunnel does not even come up at all (neither up nor down -- just doesn't show up).
Any ideas on how to further debug this issue?