sanboot iscsi fails. Any idea why?

[ingestre]

The hardware being booted is identical - In fact it's the same machine! I booted it into Clonezilla to image its local drive to the iscsi target.

I'm using a Mikrotik routerboard (brilliant router!) as the router between initiator and target so I guess I could use the packet sniffing capabilites in that to ascertain iSCSI activity on port 3260?. How do I interpret any packets captured?