Saturday, March 21, 2009

Hot Standby Router Protocol

In this episode we show a video demonstration of the hot standby router protocol.  This is a Cisco proprietary redundancy protocol.  The purpose is to allow two routers to share one virtual IP address on an access subnet/vlan.  Hosts on the subnet can use the virtual IP for their default route.  This way if one router goes down the redundant router will assume the virtual IP address, preventing a loss of connectivity to the hosts on the net.
HSRP is configured with the "standby ip" group of commands in interface configuration mode on the router.
VRRP is the virtual router redundancy protocol.  It is similar to HSRP but is vendor independent.
GLBP is the generic load balancing protocol.  It can also replace HSRP and is vendor independent.  It has the added ability to load-balance the traffic between both routers.  Using this feature you could configure approximately half the traffic to use each redundant router.
Almost all enterprise networks use HSRP, VRRP, or GLBP to provide virtual IP addresses for each access subnet.