What is VRRP and how does it differ from HSRP and GLBP for first-hop redundancy?

VRRP (Virtual Router Redundancy Protocol, RFC 5798) is an open-standard first-hop redundancy protocol that elects one master router from a group to forward traffic using a shared virtual IP. Unlike Cisco-proprietary HSRP, VRRP uses IP protocol 112 (not UDP) and allows the physical interface IP to match the virtual IP, eliminating one hop. GLBP differs by load-balancing across up to four routers simultaneously via multiple virtual MAC addresses, while VRRP and HSRP keep standby routers idle. Bangalore employers like Cisco India and Aryaka expect you to know VRRP's preemption is enabled by default (disabled in HSRP). Interview tip: mention VRRP's faster hello timer (1s default vs HSRP's 3s) when discussing convergence.