A bit of a strange one this. Coming from Cisco background, I'm trying to get my head around setting up some redundant MLT links.
I have a typical VSP9000 cluster linked by a twin 10Gb IST link. All L3 routing is done on the VSP and they are setup as VRRP.
I have an ERS5650 connected to one of the VSP9000 over 10Gb, working fine. Standard trunk connection with a bunch of VLANs tagged on the link.
Now, I want to connect a second 10Gb link to the other VSP, creating your typical triangle configuration. I have created an MLT with the same ID on both VSPs, and associated the correct port and set it to SMLT. When I create an MLT on the 5650 associating both ports, all looks OK. I can see I have an MLT of type SMLT in the VSP9000. If I ping the management address of the 5650 from a PC connected on the VSP, it works, I can unplug one fibre it works, plug it back in and unplug the other fibre, it still works, so all looks OK.
BUT, I have a second 5650 still single-attached to just one VSP, and as soon as I have the first 5650 running with dual connections, I lose all connectivity to this other 5650. As soon as I disable one of the two links on the second 5650, connection resumes on the first.