I figured out the issue - I had 2 trunk links into VLAN120 from the Juniper - as soon as I disabled the second interface it all sprang into life Now I need to try and figure out how to set up a LAG between the two MXL's in the stack and a Juniper ex3300 - I've managed to get the connectivity I need but with only a single link - as it's a remote site I want some redundancy :-) 
Hi, I have a new M100e enclosure with a PS4110xs SAN, a few blade servers and two Force10 MXL switches (switches and SAN on fabric A) I have it all set up and working fine, but using the default VLAN for everything I want to hook the switches up to a Juniper EX3300 via SFP+ ports and route the SAN subnet out so that I can remotely connect to the management IP of the EqualLogic for VMM integration  However, whenever I try and put the SAN ports into a separate VLAN - even before I look into trunking to the Juniper - I lose all connectivity on the SAN network. I've created a new VLAN (VLAN120) but as soon as I put ports into it they cannot ping each other. int vlan120 tagged te0/1 (This is the SAN port) tagged te0/12 (this is one server) tagged te0/16 (this is the other server) as soon as I do that I lose all connectivity to the SAN and the servers cannot ping each other over the iSCSI network. I've tried using 'untagged' intead of 'tagged' with the same effect. The VLAN is active (no shut)  I'm at a loss as to what the issue is. Any help gratefully received. Mark. 
VLANning issues on MXL blades