How to configure GLBP

The Gateway Load Balancing Protocol (GLBP) feature was integrated into Cisco IOS Software Release 12.2(15)T.

Highly recommend that you use the Cisco Feature Navigator to find the latest information about platform support and Cisco IOS Software image support.

Before configuring the GLBP feature, ensure that your Cisco routers can support multiple MAC addresses on the physical interfaces.

Several Ethernet (LANCE and QUICC) controllers in low-end Cisco products can only have a single unicast MAC address in their address filter.

To verify this, issue the show interfaces command, and ensure that the displayed hardware is neither LANCE nor QUICC.

These controllers do not support association of multiple MAC addresses with the interface.

Configuring basic GLBP is simple.

The basic configuration closely resembles the Hot Standby Router Protocol (HSRP) configuration.

The following sample configuration sets up two routers R1 and R2 as GLBP gateways serving the 10.1.1.0 network with 10.1.1.1 as the virtual gateway address.

This is the default gateway that would be configured on all the hosts in the 10.1.1.0 network, as shown:

R1# show running interface e0/0

ip address 10.1.1.2 255.255.255.0
glbp 1 ip 10.1.1.1

R2# show running interface e0/0
ip address 10.1.1.3 255.255.255.0
glbp 1 ip 10.1.1.1

The default mode for loadbalancing is round-robin.

This can be changed issuing the glbp 1 load-balancing host-dependent interface command.

When this command is configured, the Active Virtual gateway (AVG) ensures that a specific host gets its Address Resolution Protocol (ARP) mapping with the MAC address of the same AVF all the time.

To perform unequal load balancing, issue the glbp 1 load-balancing weighted command.

For more information on configuration, debug and verification of GLBP refer to:

Gateway Load Balancing Protocol