I've been adding storage cells to Exadatas for a long while, usually newer storage cells to a bit older Exadata.
Yesterday I had the oposite case, moving six X3-2 cells to an X-7 Exadata.
This mix of old and new storage cells is supported and can be done, but it took me a while to understand that the syntax of /opt/oracle.cellos/cell.conf had to remain as X-3.
Usually I take the cell.conf from a working cell, and edit it to match the names and IP's on the cell to add, then run ipconf with the new version of cell.conf to setup the network.
Having done this, when validating the new cell.conf it didn't pass:
Active bond ib setting value in /opt/oracle.cellos/cell.conf "yes" must match the runtime configuration: FAILED
Master interface ib0 must be defined in /opt/oracle.cellos/cell.conf : FAILED
Master interface ib1 must be defined in /opt/oracle.cellos/cell.conf : FAILED
1 configured bond over ib interfaces must be defined in /opt/oracle.cellos/cell.conf: FAILED
[Error]: Overall status of verification of /opt/oracle.cellos/cell.conf : FAILED
That led me to check and find that active-active InfiniBand, without a bond, is not supported on X3-2 cells.
If you need to change the IP's and you do that editing the cell.conf file, then you must use a copy of the same X-3 cell.conf, and change the IP's there, and use the bonded InfiniBand networks with only one IP.
Note that you may succeed to manually configure active-active with 2 IP's, without a bond, as I did, including having the cell to recognize the two interconnects and bring up all cell services, but the ipconf validation will fail, and if you are going to upgrade the cell, then patchmgr validation will fail as well.
In the end, using the X3-2 cell.conf I've changed the IP's, upgraded the cells from 22.214.171.124 to 126.96.36.199, initialize celldisks and griddisks and created a new ASM diskgroup on these six old storage cells, that provided 100TB of usable space to my customer to run some development and test databases.
State Total_MB Free_MB Req_mir_free_MB Usable_file_MB Name
MOUNTED 203497344 203493912 2826352 100333780 DATA1/