Note: If you are not sure about GLBP, please read our GLBP tutorial.
The error message indicates a possible layer2 loop and STP configuration issues. Notice that the “duplicate address” here means the MAC address.
In order to resolve this issue, issue the show interface command to verify the MAC address of the interface. If the MAC address of the interface is the same as the one reported in the error message, then it indicates that this router is receiving its own hello packets sent. Verify the spanning-tree topology and check if there is any layer2 loop. If the interface MAC address is different from the one reported in the error message, then some other device with a MAC address reports this error message.
The active virtual gateway (AVG) is responsible for answering the ARP Request for the virtual IP address. Load sharing is achieved by the AVG replying to the ARP requests with different virtual MAC addresses.
A GLBP group only has a maximum of four AVFs (means four virtual MAC addresses). If there are more than 4 gateways in a GLBP group then the rest will become Standby Virtual Forwarder (SVF) which will take the place of a AVF in case of failure.