DescriptionPort View Showing Cisco Wired Ports Going Online/Offline Frequently
Solution
Issue: Topology Port View shows the following behavior on various ports on the Cisco switch:
- All MAC addresses on a port disappear at once after several seconds, then return.
- Operational Status changing from Linkup/link down every several second. The switch itself, however, does not report the link state changing in its CLI.
If the MAC address aging time is set on the switch or VLAN to a low interval (such as 15 seconds), the mac address(es) will be removed from the switch's MAC address table every 15 seconds. Command in Cisco switch looks similar to the following example (set to 15 seconds):
mac address-table aging-time 15
If MAC Notifications are enabled, a MAC Removed trap would be sent every time the addresses are flushed, thus the port in the port view is updated to show an empty port. As soon as the switch receives the next packet from a device off the port, the MAC address is added back to the table and updated in Network Sentry.
Solution: Increase the MAC age time on switch. Default age time is typically 5 minutes.
