When a stack setup is not properly unconfigured before the stacking cables are removed, former stack nodes can become isolated.
A common symptom of this problem is that either or both ends of a stacking link show that the state is No Neighbor. This can mean that the port at either end is configured incorrectly. Some configuration errors can produce the No Neighbor state at one end and the Link Down state at the other end.
Here is an example of how an isolated node would look when you log in to it:
(pending-AAA) login: Warning: the stack has no Master node and all active nodes are operating with master-capability turned off. If you wish to reconfigure, you may log in using the failsafe account. Alternatively, you may use the special login REBOOT AS MASTER-CAPABLE with no password to force a reboot of a node with master-capability temporarily turned on.
If the show stacking command shows the stack state for a slot as Active with the “O” flag set, the node associated with that slot might be isolated from the rest of the stack by a failed node.
To fix an isolated node problem, follow these steps: