Which load-balancing algorithm does GLBP use by default?

A. Random load-balancing
B. Weighted load-balancing

C. Round-robin load-balancing

D. Host-dependent load-balancing

Explanation:

Round-robin load-balancing is the default load-balancing method used by Gateway Load Balancing Protocol (GLBP).

The active virtual gateway (AVG) can be configured to use one of three load-balancing algorithms when selecting which active virtual forwarder (AVF) MAC address to use in its ARP response.
● Round-Robin Load-Balancing: Using round-robin load-balancing, the AVG in turn points to each AVF virtual MAC address in its ARP reply (default method).
● Weighted Load-Balancing: Using weighted load-balancing, the AVG selects an AVF virtual MAC address to use in the ARP reply, proportionally based on the advertised weight value configured in a GLBP gateway.
● Host Dependant Load-Balancing: Using host-dependant load-balancing, the AVG selects an AVF virtual MAC address to use in the ARP reply based on which one the host used previously. A host will use the same AVF as long as the GLBP group is unchanged.

GLBP is a Cisco-designed protocol that provides for the dynamic use of redundant routers in a broadcast network. It differs from HSRP and VRRP in that it is not necessary to configure multiple groups to fully use redundant paths or routers. GLBP has a configurable load-balancing mechanism that will distribute the use of redundant gateways servicing a broadcast network such as an Ethernet LAN. When a host issues an ARP to resolve its gateway’s virtual IP address, the active virtual gateway (AVG) reply includes the virtual MAC address of a selected active virtual forwarder (AVF). The AVG is therefore responsible for performing load balancing, varying which virtual MAC it selects to use in the response. The AVF will own that virtual MAC as long as the gateway is active. If an AVF becomes unable to provide service as gateway, another AVF can assume ownership of the virtual MAC.

There is no random load balancing method.

GLBP and HSRP are Cisco-developed solutions. VRRP is defined in RFC 2338.

Objective:
Infrastructure Services
Sub-Objective:
Configure and verify first-hop redundancy protocols

References:
Cisco > Cisco IOS IP Application Services Configuration Guide, Release 12.4 > Part 1: First Hop Redundancy Protocols > Configuring GLBP