Which address is used in GLBP for multicast?

In the context of Gateway Load Balancing Protocol (GLBP), the address used for multicast is indeed 224.0.0.102. This specific multicast address is designated for use by GLBP routers to communicate with each other, allowing them to share load-balancing information and keep track of the status of the virtual gateway.

GLBP operates similarly to other redundancy protocols, such as HSRP and VRRP, but it has the unique feature of supporting load balancing among multiple active routers simultaneously. The use of a multicast address enables GLBP routers to efficiently utilize limited bandwidth and ensure quick updates and communication among the group of routers that are part of the same GLBP group.

Other options do not serve the specific purpose for GLBP multicast communication. 239.0.0.102 and 238.0.0.18 are not the designated addresses for GLBP. The address 224.0.0.101 is reserved for HSRP (Hot Standby Router Protocol) and not for GLBP. Understanding the correct multicast address in GLBP is crucial for configuring and troubleshooting this protocol effectively in a Cisco enterprise network environment.