H3C Technologies H3C SR8800 - Manual (Page 53)

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You can adjust the interval for sending VRRP advertisements by setting the VRRP advertisement interval
timer. If a backup receives no advertisements in a period three times the interval, the backup regards itself
as the master and sends VRRP advertisements to start a new master election.
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 (the
preemption delay time) after it receives an advertisement with the priority lower than the local priority,
then sends VRRP advertisements to start a new master election in the VRRP group and becomes the
master.
Packet format
The master multicasts VRRP packets periodically to declare its existence. 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.
Figure 12 VRRPv2 packet format
Figure 13 VRRPv3 packet format
Version Type Virtual Rtr ID Priority Count IP Addrs
Auth Type Adver Int Checksum
IP address 1
IP address n
Authentication data 1
Authentication data 2
0 7 15 23 31 3
...