After VRRP and HSRP , our last redundancy protocol is Gateway Load Balancing Protocol (GLBP). GLBP is a Cisco proprietary protocol like HSRP, but has differences surely and we will talk about how Gateway Load Balancing Protocol (GLBP) works, what is Gateway Load Balancing Protocol (GLBP).
Biggest difference of Gateway Load Balancing Protocol (GLBP) is load balancing ! That’s a huge advantage. That load balancing may be equal or unequal. GLBP uses 1 virtual IP and 2 virtual MAC addresses.
As you can see at the figure above we have two virtual macs and one virtual IP. AVG (Active virtual gateway) routes the requests with load balancing to Switch A or Switch C. Layer -2 switches like Cisco 2960 doesn’t support GLBP so you need to use a Layer-3 switch something like 3750.
GLBP CONFIGURATION
SWITCH_A(conf)#interface Fa0/0 SWITCH_A(conf-if)#glbp 1 ip 172.30.4.70 SWITCH_A(conf-if)#glbp 1 load-balancing round-robin (// Round-Robin is the default load balancing algorithm //)