The configuration of Gateway Load Balancing Protocol (GLBP) on Cisco router is easy and very much similar to that of Hot Standby Router Protocol (HSRP) and Virtual Router Redundancy Protocol (VRRP).
We will use the figure below as an example network topology.
You must configure each gateway in a GLBP group with the same group number, and at least one gateway in the GLBP group must be configured with the virtual IP address to be used by the group.
You can use the glbp group ip command to enable GLBP from the global configuration mode.
GLBP step-by-step Configuration.
R1(config-if)#ip address 10.1.2.2 255.255.255.0
R1(config-if)#glbp 1 ip 10.1.2.1
R1(config-if)#glbp 1 priority 130
R1(config-if)#glbp 1 preempt
R1(config-if)#glbp 1 load-balancing round-robin
R2(config-if)#ip address 10.1.2.3 255.255.255.0
R2(config-if)#glbp 1 ip 10.1.2.1
R2(config-if)#glbp 1 load-balancing round-robin
Explanation of the configuration above:
The glbp group number here is 1
The Router1 is configured to be the AVG and it will act as the AVF for for the group and is responsible for the virtual IP address because it has a higher priority which is 130.
The Router 2 is a member of the same GLBP group and is designated as the AVF should the AVG fail. R2 priority is default 100.
When an ARP request to the virtual ip address arrives at R1, it will respond with two different MAC address according to round-robin method, as this case may be.
Then, two clients’s (PC 1 and PC2) traffic will go through different routers. First, through R1 and the other will go through R2.
If router 1 becomes unavailable, client 1 does not lose access to CONNECTION because router 2 assumes responsibility for forwarding packets sent to the virtual MAC address of router 1 and for responding to packets sent to its own virtual MAC address. This will enable router 2 as the AVG for the group. Communication for the GLBP members will not be interrupted despite the failure of a router in the GLBP group.