VRRP Configuration
Configuring basic VRRP is a multistep process. The following are the steps to configure a basic VRRP configuration on the Cisco Nexus 7000 or 9000 Series switch:
Step 1. Enable the VRRP feature.
Step 2. Configure the VRRP group.
Step 3. Configure the virtual IP of the VRRP group.
Step 4. Configure the VRRP interface priority.
Step 5. (Optional) Configure VRRP authentication.
Step 6. (Optional) Configure VRRP object tracking.
First, you must globally enable the VRRP feature before you can configure VRRP groups. Next, you configure a VRRP group on an interface and configure the virtual IP address of the VRRP group. The virtual IP address should be in the same subnet as the IPv4 address of the interface. Next, you configure the VRRP priority on the interface. The priority range for a virtual router is from 1 to 254 (1 is the lowest priority and 254 is the highest). The default is 100 for backups and 255 for a primary router. Optionally, you can configure simple text authentication for the VRRP group. Also, you can optionally configure the VRRP group to adjust its priority based on the availability of an interface.
Gateway Load Balancing Protocol
Gateway Load Balancing Protocol (GLBP) is a Cisco-proprietary gateway resiliency solution. GLBP allows a group of Layer 3 routers to share the load of the default gateway on a LAN, and the traffic is routed to single gateway distributed across routers. Multiple routers on the LAN combine to offer a single virtual first-hop IP gateway while sharing the IP packet-forwarding load. GLBP allows full use of resources on all devices without the administrative burden of creating multiple groups. Other routers on the LAN might act as redundant GLBP gateways that become active if any of the existing forwarding gateways fail.
GLBP performs a similar function to the Hot Standby Redundancy Protocol (HSRP) and the Virtual Router Redundancy Protocol (VRRP). In HSRP and VRRP, multiple routers participate in a virtual group configured with a virtual IP address. These protocols elect one member as the active router to forward packets sent to the virtual IP address for the group. The other routers in the group are redundant until the active router fails. GLBP performs an additional load-balancing function that the other protocols do not provide. GLBP load-balances over multiple routers (gateways) using a single virtual IP address and multiple virtual MAC addresses. GLBP shares the forwarding load among all routers in a GLBP group instead of allowing a single router to handle the whole load while the other routers remain idle. You configure each host with the same virtual IP address, and all routers in the virtual group participate in forwarding packets. GLBP members communicate between each other using periodic hello messages.
Figure 3-10 illustrates GLBP forwarding.
Figure 3-10 GLBP Forwarding