GLBP

GLBP Overview

GLBP (Gateway Load Balancing Protocol) is an another First Hop Redundancy Protocol. It is a Cisco proprietary protocol like HSRP. So ,you can only use Gateway Load Balancing Protocol on Cisco devices. Here, we will learn the details of the protocol and we will also learn GLBP Configuration in another lesson.

GLBP has a key benefit that HSRP and VRRP do not have. This benefit is load-balancing. Gateway Load Balancing Protocolprovides load balancing over multiple routers using a single Virtual IP address and multiple Virtual MAC Addresses. Each host is configured with the same Virtual IP address, and all routers in the virtual router group participate in forwarding packets. According to the assigned MAC, each one does the forwaring.

Gateway Load Balancing Protocol supports up to 1024 virtual routers meaning GLBP groups on each physical interface of a router. And for each GLBP group, 4 virtual forwarders are supported.

Main Differences Between GLBP and HSRP/VRRP

In this lesson, I think it will be better to compare GLBP with HSRP (Hot Standby Router Protocol) and VRRP. So, you can easily understand the difference between Gateway Load Balancing Protocol and the other two protocol.

First of all, while using HSRP and VRRP, there is only one Active Router at the same time as I mentined before. The traffic only goes through on this Active Router. Whenever the Active Router becomes down, the Standby Router becames active and it is used for traffic flow. But with GLBP, the situation is different and this is more efficient. In Gateway Load Balancing Protocol, there can be more than one Active Router. So you can use these routers at the same.

Secondly, we can configure groups for HSRP and VRRP on routers, and we can configure one router as an Active Router for one group and a Standby Router for another group. So it looks like a basic load-balancing. But this is not widely used in reality. With Gateway Load Balancing Protocol, we can use more active routers and we can use them with different load balancing adjustments. So the traffic goes through all of them with different ratios.

At this point, let’s explore how Gateway Load Balancing Protocol works.

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How GLBP Works?

GLBP mechanims has different routers that has different roles like other First Hop Redundancy Protocols (FHRPs). These GLBP routers types are:

• AVG(Active Virtual Gateway)
• AVF(Active Virtual Forwarder)

And one addition name can be used as SVG(Standby Virtual Gateway) for backup AVG.