The FWWN is the Fabric WWN (world wide name) for the switch port. The nWWN is the Node WWN.
The NWWN was designed to represent a complete box on a SAN. The NWWN may be the same for several (port) PWWNs.
IE: a storage array may have 4 FC ports.
array nwwn - 432
Port 1 - pwwn 123 -> MDS 1/1 fwwn 789
Port 2 - pwwn 345 -> MDS 1/2 fwwn 78a
port 3 - pwwn 678 -> MDS 1/3 fwwn 78b
port 4 - pwwn 9ab -> MDS 1/4 fwwn 78c
Frames from array port 1 will use nwwn 432 and pwwn 123
Frames from array port 4 will use nwwn 432 and pwwn 9ab
Not all implementations use the NWWN as it was intended. Some host HBAs will use a unique NWWN for each HBA installed in the server.
If you need to determine the MDS fwwn, use the command 'show fcs database' and you will see the switch port fwwn, and the attached PWWN if there is one.
If you need to determine an attached devices nwwn, use the command 'show fcns data detail vsan x' and scroll down to the desired entry. You will see the pwwn and nwwn that the device used to register.
FCIDs in the MDS are allocated by pwwn of the attaching device. If you login an HBA to port 1/1 and them move it to port 1/2 (assuming same vsan) the HBA will get the same FCID on port 1/2.
Hope this helps,
Mike
