I ran into this in my lab when upgrading a switch which caused a fabric-segmentation and obviously the release notes of a previous version show:
Other Important Notes and Recommendations
Management Server Platform Capability support changes in FOS v6.4
FOS v6.4 no longer automatically enables the Management Server (MS) Platform capability when a switch attempts to join a fabric that has these services enabled. This prevents a FOS v6.4 switch from joining such a fabric, and ISL will be disabled with a RAS log message. To allow a FOS v6.4 switch to join such fabrics msPlMgmtActivate command should be used to enable the Management Server platform services explicitly.
So on a switch it looks like this:
Sydney_ILAB_7k82:admin> portshow 1
portDisableReason: Implicit Platform Service Enable blocked
portFlags: 0x4021 PRESENT U_PORT DISABLED LED
portState: 2 Offline
portPhys: 6 In_Sync portScn: 2 Offline
port generation number: 4
And in the eventlog you’ll see this:
2014/09/02-06:41:15, [MS-1026], 3060, FID 128, WARNING, Sydney_ILAB_7k82, MS Platform disabled port 1 domain 143 to block enabling Platform service through merge operation.
This results in:
06:41:05.171043 No FID or BS conflict with domain 76 A2,NA A2,NA NA NA
06:41:05.171046 No conflict,lf=128,m=0,f=128,b=0,e=1 A2,NA A2,NA NA NA
06:41:05.508390 SCN Domain 20 available A2,NA A2,NA NA NA
06:41:05.508597 *Snd inquiry (20) A2,NA A2,NA NA NA
06:41:05.508627 Dom 20 name BR4100_IP116 A2,NA A2,NA NA NA
06:41:05.508716 *Snd inquiry 2 (20) A2,NA A2,NA NA NA
06:41:05.508725 Dom 20 A2,NA A2,NA NA NA
06:41:05.522852 No FID or BS conflict with domain 20 A2,NA A2,NA NA NA
06:41:05.522854 No conflict,lf=128,m=0,f=0,b=0,e=1 A2,NA A2,NA NA NA
06:41:13.804414 SCN Fabric stable A2,NA A2,NA NA NA
06:41:15.281404 SCN Port Offline;g=0x4 A2,P3 A2,P0 1 NA
06:41:15.281417 *Snd port state: P0 A2,P0 A2,P0 1 NA
06:41:15.281454 *Removing all nodes from port A2,P0 A2,P0 1 NA
06:41:15.281573 No next principal pt A2,NA A2,NA NA NA
06:41:15.281859 Reconfig due to Offline(port 1) A2,NA A2,NA NA NA
06:41:15.281876 *Canceling All Node Timers A2,NA A2,NA NA NA
After turning the msplatform service back on via the command msplmgmtactivate and portenable
2014/09/02-06:44:40, [MS-1022], 3061, FID 128, INFO, Sydney_ILAB_7k82, Management Server Platform Service Activated.
The ISL came back online and a successful merge was conducted.
Just so you see that many things are actually mentioned in the documentation.