R3204P16-HP Load Balancing Module High Availability Configuration Guide-6PW101

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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.
2. VRRP preemption delay timer
To avoid members in a VRRP group from changing their states frequently and make backups have
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 finally becomes the
master.
Format of VRRP packets
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.
Figure 3 sho
ws the format of a VRRPv2 packet.
Figure 3 Format of a VRRPv2 packet
As shown in Figure 3, an IPv4-based VRRP packet consists of the following fields:
• Version—Version number of the protocol, 2 for VRRPv2.
• Type—Type of the VRRP packet. Only one VRRP packet type is present, that is, VRRP advertisement,
which is represented by 1.
• Virtual Rtr ID (VRID)—Serial number of the virtual router, that is, serial number of the VRRP group.
It ranges from 1 to 255.
• Priority—Priority of the router in the VRRP group, in the range 0 to 255. A greater value represents
a higher priority.
• Count IP Addrs—Number of virtual IP addresses for the VRRP group. A VRRP group can have
multiple virtual IP addresses.
• Auth Type—Authentication type. 0 means no authentication, 1 means simple text authentication,
and 2 means MD5 authentication.
• Adver Int—Interval for sending advertisements. For VRRPv2, the interval is in seconds and defaults
to 1.
• Checksum—16-bit checksum for validating the data in VRRP packets.
• IP Address—Virtual IP address entry of the VRRP group. The Count IP Addrs field defines the number
of the virtual IP addresses.
• Authentication Data—Authentication key. This field is used only for simple authentication and is 0
for any other authentication modes.
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 23 313