Assuming you are running cDoT 8.3 or higher, you are likely encountering the new "Selective LUN Mapping" feature. This feature was added in cDoT 8.3 to address the multiplication of paths across large clusters that can impact server based total and per LUN path limits.
From the SAN Administration Guide...
Selective LUN Map
Selective LUN Map (SLM) reduces the number of paths from the host to the LUN. With SLM, when a new LUN map is created, the LUN is accessible only through paths on the node owning the LUN and its HA partner.
SLM enables management of a single igroup per host and also supports nondisruptive LUN move operations that do not require portset manipulation or LUN remapping.
Portsets can be used with SLM just as in previous versions of Data ONTAP to further restrict access of certain targets to certain initiators . When using SLM with portsets, LUNs will be accessible on the set of LIFs in the portset on the node that owns the LUN and on that node's HA partner.
Beginning with Data ONTAP 8.3 SLM is enabled by default on all new LUN maps. For LUNs created prior to Data ONTAP 8.3, you can manually apply SLM by using the lun mapping remove-reporting-nodes command to remove the LUN reporting nodes and restrict LUN access to the LUN owning node and its HA partner.
I ran into the same situation myself when adding nodes 5 and 6 to a cluster, moving some LUNs there, and then not seeing direct paths. Mine was FCP, but since this applies at the LUN mapping level it would be just as applicable to iSCSI as well.
The commands of interest to you are:
lun mapping show -field reporting-nodes -vserver <SVM> -path <lun-path>
lun mapping add-reporting-nodes ...
lun mapping remove-reporting-nodes ...
SLM provides for very specific path control and in conjunction with portsets can limit path proliferation especially as the number of potential ports increases and the number of allowed hosts in a SAN cluster increases with refreshed hardware and ONTAP 9.1.
Hope this helps.
Bob Greenwald
Senior Systems Engineer | cStor
NCIE SAN ONTAP, Data Protection
Kudos and accepted solutions are always accepted.