Gateway Load Balancing Protocol (GLBP)
Gateway Load Balancing Protocol (GLBP) is an First Hop Redundancy Protocol used for creating gateway redundancy in a subnet. It is similar in functionality to Hot Standby Router Protocol (HSRP) and Virtual Router Redundancy Protocol (VRRP).
It is used to create a virtual gateway that can be used by hosts in a particular subnet.
One of the key differences of GLBP is that it can natively do load balancing between configured gateways without the group configuration that HSRP/VRRP use.
Links:
https://networklessons.com/cisco/ccie-routing-switching/glbp-gateway-load-balancing-protocol