F3726, F3211, F3174, R5135, R3816-HP Firewalls and UTM Devices High Availability Configuration Guide-6PW100

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2. VRRP preemption delay timer
To avoid frequent state changes among members in a VRRP group and provide the backups
enough time to collect information (such as routing information), each backup waits for a period
of time called the preemption delay time. The backup waits this period of time after it receives an
advertisement with the priority lower than the local priority, then it sends VRRP advertisements to
start a new master election in the VRRP group and becomes the master.
228BPacket format
The master periodically multicasts VRRP packets to declare its presence. VRRP packets are also used for
checking the parameters of the virtual router and electing the master.
VRRP packets are encapsulated in IP packets, with the protocol number being 112.
478HFigure 3 shows the
VRRPv2 packet format and
479HFigure 4 shows the VRRPv3 packet format.
Figure 3 VRRPv2 packet format
Figure 4 VRRPv3 packet format
A VRRP packet comprises the following fields:
• Version—Version number of the protocol, 2 for VRRPv2 and 3 for VRRPv3.
• Type—Type of the VRRPv2 or VRRPv3 packet. It must be VRRP advertisement, represented by 1.
...
Version Type Virtual Rtr ID Priority Count IPv6 Addrs
Auth Type Adver Int Checksum
IPv6 address 1
Authentication data 1
Authentication data 2
IPv6 address n
0 7 15 23 313