Core Issue
When Hot Standby Router Protocol (HSRP) is running on a device, the %HSRP-4-DUPADDR:Duplicate address [IP_address] on [chars], sourced by [enet] error message can appear on the console if the IP address in an HSRP message received on the specified interface is the same as the IP address of the router receiving the message. The most likely cause of this condition is a network loop or a misconfigured switch that is causing the router to see its own HSRP hello messages.
Resolution
Check the configurations on all the HSRP routers to ensure that the interface IP addresses are unique. Check that no Layer-2 loops exist. If port channels are configured, check that the switch is configured correctly for port channels. Issue the standby use-bia command so that the error message displays the interface MAC address of the sending router, which can be used to determine if the error message is caused by a misconfigured router or a network loop.
For more information, refer to Understanding and Troubleshooting HSRP Problems in Catalyst Switch Networks.
Other Errors, Warnings, and Log Messages
HSRP - "%STANDBY-3-DUPADDR"
