NHRP: GLBP config - Cisco
Technology: Routing
Area: NHRP
Vendor: Cisco
Software: 12.X , 15.X
Platform: Catalyst platforms, Routing platforms

Gateway Load Balancing Protocol (GLBP) is one of the NHRP kind protocols that protects traffic from a router or circuit failure. GLBP behaves very similar to Hot Standby Router Protocol (HSRP) and Virtual Router Redundancy Protocol (VRRP). GLBP communicates over Layer 2.

To configure GLBP (basic configuration), use the following command on first router (primary):

Router1(config)# interface GigabitEthernet 0/1
Router1(config-if)#ip address 20.1.1.2 255.255.255.0
Router1(config-if)# glbp 10 ip 20.1.1.1
Router1(config-if)# glbp priority 150
Router1(config-if)# exit

Configure the backup GLBP router:

Router2(config)# interface GigabitEthernet 0/1
Router2(config-if)#ip address 20.1.1.3 255.255.255.0
Router2(config-if)# glbp 10 ip 20.1.1.1
Router2(config-if)# exit

Hosts will use 20.1.1.1 as active address (default gateway). Default GLBP priority is 100, the higher wins and is elected on active router. If priorities are the same, the higher priority wins the active gateway election.