Case Study: After the Active and Standby ACs Are Upgraded and Restarted, APs Go Online on the Standby AC but Not on the Active AC
Symptom
The active and standby ACs are restarted at the same time after the software package is replaced. After the restart, the AP goes online on the standby AC but does not go online on the active AC, and no dual-link is established.
Relevant Alarms and Logs
None
Cause Analysis
After the software packages of the active and standby ACs are replaced at the same time and the ACs are restarted, the standby AC runs normally first. However, the active AC is not started after the AP selects an AC. Therefore, the AP sets up a link with the standby AC. In addition, the dual-link switch is disabled on the standby AC. Therefore, dual links cannot be set up.
Procedure
- Check whether the dual-link switch is enabled on the master AC. No problem is found.
- Check whether the IP address of the standby AC is the same as that of the active AC.
- Check whether the standby AC is running properly.
- Check the dual-link switch on the standby AC. It is found that the dual-link switch is not turned on.
Suggestion and Summary
The possible cause is that the dual-link backup function is disabled on the standby AC. Therefore, dual links are not set up. However, the AP sets up a link with the standby AC, which is different from the link set up between the AP and the active AC, but does not set up a link with the active AC.
Further analysis shows that the AP sets up a link with the standby AC after the standby AC is restarted due to software package replacement. However, the dual-link backup function is not enabled on the standby AC. As a result, the AP sets up a link with the standby AC.