7.5.2 Fault and recovery of stack link

(1) Stack link failure

The following figure shows the behavior when all stack links fail.

Figure 7-8: Stack link failure

If all stack links fail, the master and backup switches will not be able to recognize adjacent member switches. As a result, one stack is divided into two stacks, the master switch remains the master switch, and the backup switch is switched to the master switch.

In this case, the same IP address and device MAC address are used in the two stacks, so communication cannot be performed correctly because of address overlap.

If there are two stack links, the stack link continues to operate on the remaining stack links even if a failure occurs in a particular stack link. However, if the remaining stack link fails, the stack will be split into two. If one of the stack links fails, immediately restore the stack link.

(2) Stack link recovery

The following figure shows the operation when the stack link is recovered from a failure.

Figure 7-9: Stack link recovery

When the stack link recovers from a failure, the member switches that were split into two stacks recognize each other and operate on one stack.