Merging stack fragments
When two fragments have the same stack-id, the merge of the fragments is almost always allowed regardless of the merge policy. The Commander and Standby of the merged stack are selected based on the election rules. All switches in the previously inactive fragment or fragments reboot, and join the Active fragment as Members.
If both fragments are Inactive, then an election process occurs: the two (or more) Commanders in the fragments are compared, and the Commander is selected using the following criteria:
Highest Stack Rev.
If the stack rev is the same for both, then choose the switch with the highest configured priority.
If the priorities are the same for both, then choose the switch with the highest OS revision.
If the OS revisions are the same, then choose the switch with the longest uptime.
If the uptimes are the same, then choose the switch with the lowest MAC address.