So im studying redundancy features, especially gateway redundancy features. I think this is some impressing technology. Basically there are three versions, HSRP (cisco proprietary), VRRP (IEEE Standard) and GLBP (cisco proprietary). HSRP was introduced in 1994, and VRRP in 1999, GLBP is alot newer, introduced in 2005.
HSRP stands for Hot Standby Router Protocol, VRRP is Virtual Router Redundancy Protocol and finally GLBP is Gateway Load Balancing Protocol.
Given the incredible redundancy they each perform, they are incredible simple to setup. It works by creating a “virtual IP” address along with a “virtual MAC” address. (Mac will become: 0000.0c07.acXX where XX is the HSRP group number).
VRRP is basically the same, but is a standard, also as standard provides some faster timers ~ which will equal faster convergence.
GLBP is somewhat different though, in that it utilizes all links in some manner. an AVG (Active Virtual Gateway) is choosen to manage a bunch of MAC addresses. Each AVF (Active Virtual Forwarder) then gets a mac address. When an ARP request is received, the AVG hands out one of these MAC addresses defined by how you want the load balancing to take place. You can choose between host-dependent, round-robin and weighted, where you can rate each router/switch according to the traffic flow.
All in all, very cool stuff 🙂