3Com Switch 8800 Advanced Software V5 Configuration Guide

764 CHAPTER 54: VRRP CONFIGURATION
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 231 IPv4-based VRRP packet format
As shown in Figure 231, 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. The priority of 0 is reserved for special
purposes, while 255 is reserved for the IP address owner.
■ 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.
...
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