Configuration for GLBP

Before diving into the load balancing methods within GLBP, let’s start with the basic configuration of GLBP.

RouterA(config)# interface GigabitEthernet0/0
RouterA(config-if)# ip address
RouterA(config-if)# glbp 1 ip
RouterA(config-if)# glbp 1 priority 100
RouterA(config-if)# glbp 1 preempt

In this initial configuration, we’ve set up RouterA for GLBP with group 1, assigned it an IP address, set the virtual IP address, and configured a priority of 100, making it the initial Active Virtual Gateway (AVG). The “preempt” command ensures RouterA becomes AVG again when it recovers.

Load Balancing in GLBP

GLBP offers three load balancing methods: round robin, weighted, and host-dependent. Each method serves different network requirements. Let’s explore these methods and their configurations.

Round Robin Load Balancing

This is the default load balancing method in GLBP. In round robin, each virtual forwarder MAC address responds sequentially for the virtual IP address. It evenly distributes traffic among all active virtual forwarders. This is suitable for scenarios where all routers have similar capacities and should share traffic equally.

RouterA(config-if)# glbp 1 load-balancing round-robin

Weighted Load Balancing

In weighted load balancing, you assign weights to each device within the GLBP group. These weights define the ratio of load balancing between devices. This method allows you to allocate a larger weight to more powerful routers capable of handling heavier traffic loads. Weighted load balancing is particularly useful in heterogeneous network environments with routers of varying capacities.

RouterA(config-if)# glbp 1 load-balancing weighted
RouterA(config-if)# glbp 1 weighting 150
RouterB(config-if)# glbp 1 weighting 100

Host-Dependent Load Balancing

Host-dependent load balancing uses the host MAC address to determine which virtual forwarder MAC should handle the incoming packet. This method ensures that the host consistently uses the same virtual MAC address, as long as the number of virtual forwarders in the group remains constant. Host-dependent load balancing is suitable for applications where session persistence or stickiness is required, such as in some web applications.

RouterA(config-if)# glbp 1 load-balancing host-dependent


GLBP’s load balancing methods, including round robin, weighted, and host-dependent, offer a range of options to suit different network requirements. Understanding and configuring these methods is crucial for network professionals pursuing the CCNP ENCOR certification, as it enables efficient, resilient, and high-performing networks tailored to specific needs.


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