H3C LS-3100-52P-OVS-H3 Operation Manual - page 1815
1-4
VRRP advertisement interval timer
The master in a VRRP group sends VRRP advertisements periodically to inform the other routers in the
VRRP group that it operates properly.
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
In an unstable network, a backup can fail to receive the packets from the master due to network
congestion and thus the members in the group change their states frequently. Set the VRRP
preemption delay timer to address the problem.
With the VRRP preemption delay timer set, if a backup receives no advertisement in a period three
times the advertisement interval and then the preemption delay, it considers that the master fails. In this
case, the backup regards itself as the master and sends VRRP advertisements to start a new master
election in the VRRP group.
Format of VRRP Packets
VRRP uses multicast packets. The router acting as the master sends VRRP packets periodically to
declare its existence. VRRP packets are also used for checking the parameters of the virtual router and
electing the master.
IPv4-based VRRP packet format
Figure 1-3 Format of IPv4-based VRRP 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 VRRP packet. Only one VRRP packet type is present, that is, VRRP
advertisement, 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 represents
a higher priority.
z
Count IP Addrs: Number of virtual IP addresses for the VRRP group. A VRRP group can have
multiple virtual IP addresses.
z
Auth Type: Authentication type. 0 means no authentication, 1 means simple text authentication,
and 2 means MD5 authentication.