114• Auth Type: Authentication type. 0 means no authentication, 1 means simple textauthentication, and 2 means MD5 authentication. VRRPv3 does not support MD5authentication.• Adver Int: Interval for sending advertisement packets. For VRRPv2, the interval is in secondsand defaults to 1; for VRRPv3, the interval is in centiseconds and defaults to 100.• Checksum: 16-bit checksum for validating the data in VRRP packets.• IP Address/IPv6 Address: Virtual IPv4 or IPv6 address entry of the VRRP group. The Count IPAddrs or Count IPv6 Addrs field defines the number of the virtual IP v4 or IPv6 addresses.• Authentication Data: Authentication key. This field is used only for simple authentication andis 0 for any other authentication modes.Principles of VRRP• With VRRP enabled, the routers decide their respective roles in the VRRP group by priority.The router with the highest priority becomes the master, and the others are the backups. Themaster sends VRRP advertisements periodically to notify the backups that it is workingproperly, and each of the backups starts a timer to wait for advertisements from the master.• In preemptive mode, when a backup receives a VRRP advertisement, it compares the priorityin the packet with that of its own. If the priority of the backup is higher, the backup becomesthe master; otherwise, it remains a backup.• In non-preemptive mode, the router in the VRRP group remains as a master or backup aslong as the master does not fail. The backup does not become the master even if the backupis configured with a higher priority.• If the timer of a backup expires but the backup still does not receive any VRRPadvertisement, it considers that the master fails. In this case, the backup considers itself themaster and sends VRRP advertisements to start a new master election.VRRP trackingTracking a specified interfaceThe interface tracking function expands the backup functionality of VRRP. It provides backup notonly when the interface to which a VRRP group is assigned fails but also when other interfaces(such as uplink interfaces) on the router become unavailable.If the uplink interface of a router in a VRRP group fails, normally the VRRP group cannot be awareof the uplink failure. If the router is the master of the VRRP group, hosts on the LAN are not able toaccess the external network because of the uplink failure. You can solve the problem through thefunction of tracking a specified interface. In this case, it is the uplink interface. After you configureto monitor the uplink interface, when the uplink interface goes down, the priority of the master isautomatically decreased by a specified value and a higher priority router in the VRRP groupbecomes the master.Tracking a track entryBy monitoring a track entry, you can:
