1-4VRRP advertisement interval timerThe master in a VRRP group sends VRRP advertisements periodically to inform the other routers in theVRRP group that it operates properly.You can adjust the interval for sending VRRP advertisements by setting the VRRP advertisementinterval timer. If a backup receives no advertisements in a period three times the interval, the backupregards itself as the master and sends VRRP advertisements to start a new master election.VRRP preemption delay timerTo avoid members in a VRRP group from changing their states frequently and make backups haveenough time to collect information (such as routing information), each backup waits for a period of time(the preemption delay time) after it receives an advertisement with the priority lower than the localpriority, then sends VRRP advertisements to start a new master election in the VRRP group and finallybecomes the master.Packet FormatThe master multicasts VRRP packets periodically to declare its existence. VRRP packets are also usedfor checking the parameters of the virtual router and electing the master.Figure 1-3 Format of a VRRPv2 packet ...As shown in Figure 1-3, an IPv4-based VRRP packet consists of the following fields:z Version: Version number of the protocol, 2 for VRRPv2.z Type: Type of the VRRPv2 packet. Only one VRRP packet type is present, that is, VRRPadvertisement, which is represented by 1.z Virtual Rtr ID (VRID): Serial number of the virtual router, that is, serial number of the VRRP group.It ranges from 1 to 255.z Priority: Priority of the router in the VRRP group, in the range 0 to 255. A greater value representsa higher priority.z Count IP Addrs: Number of virtual IP addresses for the VRRP group. A VRRP group can havemultiple virtual IP addresses.z Auth Type: Authentication type. 0 means no authentication, 1 means simple text authentication,and 2 means MD5 authentication.z Adver Int: Interval for sending advertisement packets, in seconds. The default is 1.z Checksum: 16-bit checksum for validating the data in VRRP packets.z IP Address: Virtual IP address entry of the VRRP group. The Count IP Addrs field defines thenumber of the virtual IP addresses.
