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Gateway Load Balancing Protocol


Gateway Load Balancing Protocol (GLBP) can be used to replace HSRP in environments where you would like to load balance between multiple nodes, instead of having an active/standby pair.

In order to enhance on the capabilities of Hot Standby Router Protocol (HSRP), Cisco developed GLBP. GLBP provides automatic, first-hop gateway load balancing, which allows for more efficient resource usage and reduced administrative costs. It is an extension of HSRP and specifies a protocol that dynamically assigns responsibility for a virtual IP address and distributes multiple virtual MAC addresses to members of a GLBP group.

In campus networks, Layer 3 VLAN interfaces act as the gateway for the hosts. These Layer 3 VLAN interfaces from different switches are load balanced using GLBP. Layer 3 interfaces from multiple switches form one GLBP group. Each group contains one unique virtual IP address.

Supervisor 720 can have a maximum of 1024 GLBP groups (group numbers 0 to 1023). Supervisor 2 supports only one GLBP group. A GLBP group can have a maximum of 4 members. It means that GLBP can load balance up to 4 gateways