Principles of vrrp, Vrrp tracking – H3C Technologies H3C S7500E Series Switches User Manual
Page 139
10-6
z
Version: Version number of the protocol, 2 for VRRPv2 and 3 for VRRPv3.
z
Type: Type of the VRRPv2 or VRRPv3 packet. Only one VRRP packet type is present, that
is, VRRP advertisement, which is represented by 1.
z
Virtual Rtr ID (VRID): ID of the virtual router, that is, ID 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/Count IPv6 Addrs: Number of virtual IPv4 or IPv6 addresses for the VRRP
group. A VRRP group can have multiple virtual IPv4 or IPv6 addresses.
z
Auth Type: Authentication type. 0 means no authentication, 1 means simple text
authentication, and 2 means MD5 authentication. VRRPv3 does not support MD5
authentication.
z
Adver Int: Interval for sending advertisement packets. For VRRPv2, the interval is in
seconds and defaults to 1; for VRRPv3, the interval is in centiseconds and defaults to 100.
z
Checksum: 16-bit checksum for validating the data in VRRP packets.
z
IP Address/IPv6 Address: Virtual IPv4 or IPv6 address entry of the VRRP group. The Count
IP Addrs or Count IPv6 Addrs field defines the number of the virtual IP v4 or IPv6
addresses.
z
Authentication Data: Authentication key. Currently, this field is used only for simple
authentication and is 0 for any other authentication modes.
Principles of VRRP
z
Routers in a VRRP group determine their roles by priority and IP address. The router with
the highest priority is the master, and the others are the backups. If the routers have the
same priority, the one with the highest IP address becomes the master. The master
periodically sends VRRP advertisements to notify the backups that it is working properly,
and each of the backups starts a timer to wait for advertisements from the master.
z
In preemptive mode, when a backup receives a VRRP advertisement, it compares the
priority in the packet with its own priority. If the priority of the backup is higher, the backup
becomes the master; otherwise, it remains as a backup. With the preemptive mode, a
VRRP group always has a router with the highest priority as the master for packet
forwarding.
z
In non-preemptive mode, a router in the VRRP group remains as a master or backup as
long as the master does not fail. A backup does not become the master even if it is
configured with a higher priority. The non-preemptive mode helps avoid frequent
switchover between the master and backups.
z
If the timer of a backup expires but the backup still does not receive any VRRP
advertisement, it considers that the master fails. In this case, the backup considers itself as
the master and sends VRRP advertisements to start a new master election.
VRRP Tracking