BigIron RX Series Configuration Guide 44553-1001986-01Overview of VRRP 17NOTEYou can provide more redundancy by also configuring a second VRID with Router2 as the Owner andRouter1 as the Backup. This type of configuration is sometimes called Multigroup VRRP.Master router electionVirtual routers use the VRRP priority values associated with each VRRP router to determine whichrouter becomes the Master. When you configure an Owner router, the device automatically sets theits VRRP priority to 255, the highest VRRP priority. The router in the virtual router with the highestpriority becomes the Master. Other routers become the backup and can be assigned priorities 3 –254. The default priority value is 100.Virtual routers use VRID Hello messages to determine if a Master router is available. They sendHello messages to IP Multicast address 224.0.0.18 at a specified frequency. The Backup routerswaits for a duration of time for a Hello message from the Master. This duration is called the DeadInterval. If a Backup router does not receive a Hello message by the time the dead interval expires,the Backup router assumes that the Master router is dead. the Backup router with the highestpriority becomes the Master router. Once the Owner router becomes available, it becomes theMaster router and the current Master router returns to being a backup router.Pre-emptionIf the pre-emption feature is enabled, a Backup router that is acting as the Master can bepre-empted by another Backup router that has a higher priority. This can occur if you add a newBackup while the Owner is still available and new Backup router has a higher priority than theBackup router that is acting as Master.Virtual router MAC addressWhen you configure a VRID, the software automatically assigns its MAC address as the virtualrouter’s MAC address. The first five octets of the address are the standard MAC prefix for VRRPpackets, as described in RFC 3768. The last octet is the VRID. THE VRID number becomes thefinal octet in the virtual router’s virtual MAC address. For example, the MAC address for VRID is000.5e00.0101.When the virtual router becomes the Master router, it broadcasts a gratuitous ARP requestcontaining the virtual router’s MAC address for each IP address associated with the virtual router.In Figure 85, Router1 sends a gratuitous ARP with MAC address 00-00-5e-00-01-01 and IP address192.53.5.1. Hosts use the virtual router’s MAC address in routed traffic they send to their defaultIP gateway (in this example, 192.53.5.1).Brocade enhancements of VRRPBrocade enhanced VRRP by adding the following options:• Track Ports and Track Priority• Suppression of RIP Advertisements for Backed Up Interfaces• Authentication• VRRP’s operation is independent of RIP, OSPF, and BGP
