This message means that the Enhanced Address Recognition Logic (EARL) was not able to set the Content Addressable Memory (CAM) aging time for the VLAN to 15 seconds, which is fast aging.
The reason the EARL cannot set the VLAN to fast aging is because the VLAN is already in fast aging and the aging timer set process is blocked. This message is informational and does not necessarily indicate a problem.
The default CAM aging time is five minutes, which means that the switch flushes its table of learned MAC addresses every five minutes. This ensures that the MAC address table (the CAM table) has current entries.
Fast aging temporarily sets the CAM aging time to 15 seconds and is used in conjunction with the Topology Change Notification (TCN) process. When a topology change occurs, the CAM table is flushed faster to compensate for the topology change that occurs.
The most common change of TCNs are client PCs connected directly to a switch. When the PC is powered up or down, the switch port changes state and the switch kicks in the TCN process because it does not know that the connected device is a PC. It just knows that the port has changed state. That is why portfast is used for PC connections. Portfast suppresses TCNs for that port.
If you want to suppress unnecessary TCNs, issue the set spantree portfast mod_num/port_num enable command.
Note: Only enable portfast on ports with a single end station connected, like a workstation or server.