Format Of Vrrp Packets - 3Com MSR 50 Series Configuration Manual

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 585 IPv4-based VRRP packet format
0 3 7
Version Type
Auth Type
As shown in Figure 585, 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): Number of the virtual router, that is, number of the
■
standby group. It ranges from 1 to 255.
Priority: Priority of the router in the standby group, in the range 0 to 255. A
■
greater value represents a higher priority.
Count IP Addrs: Number of virtual IP addresses for the standby group. A
■
standby group can have multiple virtual IP addresses.
Auth Type: Authentication type. 0 means no authentication, 1 means simple
■
authentication, and 2 means MD5 authentication.
Adver Int: Interval for sending advertisement packets, in seconds. The default is
■
1.
Checksum: 16-bit checksum for validating the data in VRRP packets.
■
IP Address: Virtual IP address entry of the standby group. The allowed number
■
is given by the Count IP Addrs field.
Authentication Data: Authentication key. Currently, this field is used only for
■
simple authentication and is 0 for any other authentication modes.
15
Virtual Rtr ID
Adver Int
IP address 1
IP address n
Authentication data 1
Authentication data 2
Introduction to VRRP
23
Priority Count IP Addrs
Checksum
1975
31