H3C Technologies H3C SecPath F1000-E - Manual (Page 833)

4
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 shows 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. Currently, this field is used only for simple authentication
and is 0 for any other authentication modes.