Virtual IP Address for Transparent Failover

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The protocol that advertises a virtual IP address to facilitate transparent failover of a Cisco routing device is called First Hop Redundancy Protocol (FHRP).

FHRP is a group of protocols that are used to provide redundancy and high availability for IP networks. It operates by creating a virtual IP address that is shared among a group of routers, with one router acting as the active router and the others acting as standby routers. The active router is responsible for forwarding traffic to the virtual IP address, while the standby routers monitor the health of the active router and take over if it fails.

FHRP includes several protocols, such as Hot Standby Router Protocol (HSRP), Virtual Router Redundancy Protocol (VRRP), and Gateway Load Balancing Protocol (GLBP). These protocols are designed to work with different types of network topologies and devices.

HSRP is a Cisco proprietary protocol that is commonly used in enterprise networks. It operates by creating a virtual IP address and a virtual MAC address that are shared among a group of routers. The active router is responsible for forwarding traffic to the virtual IP address, while the standby routers monitor the health of the active router and take over if it fails.

VRRP is a standard protocol that is supported by multiple vendors. It operates in a similar way to HSRP, but it allows multiple active routers to share the forwarding load, providing better scalability and load balancing.

GLBP is another Cisco proprietary protocol that provides load balancing among a group of routers. It operates by assigning multiple virtual IP addresses to a group of routers, with each router acting as the active router for a different virtual IP address.

In conclusion, the protocol that advertises a virtual IP address to facilitate transparent failover of a Cisco routing device is First Hop Redundancy Protocol (FHRP), which includes protocols such as HSRP, VRRP, and GLBP.