User's Manual

65-2
protocols. Compared with NDP, VRRP provides a fast default gateway switch. In VRRP, backup routers can
take up the unavailable master router in about 3 seconds (default parameter), and this process needs no
interaction with hosts, which means being transparent to hosts.
65.1.1 The Format of VRRPv3 Message
VRRPv3 has its own message format, VRRP messages are used to communicate the priority of routers and
the state of Master in the backup group, they are encapsulated in IPv6 messages to send, and are sent to the
specified IPv6 multicast address. The format of VRRPv3 message is shown in Graph 1. The source address
of the IPv6 message encapsulating the VRRPv3 message is the local address of the outbound interface of the
message, and the destination address of it is the IPv6 multicast address(the multicast allocated to VRRPv3 is
FF02:0:0:0:0:0:0:12). The number of hops should be limited to 255, and the next message head is
112(representing a VRRP message).
The meaning of each field in a VRRPv3 message is shown as follows:
Version: The version of VRRPv3, whose value is 3;
Type: The type of VRRP messages. There is only one type: ADVERTISEMENT, and its value is 1;
Virtual Rtr ID：The ID of the virtual router;
Priority：Priority, ranging from 0 to 255;
Count IPv6 Addr：The number of IPv6 addresses in a VRRPv3 message, the minimum of which is 1;
Rsvd：Reserved field, whose value is 0;
Adver Int：The advertisement interval of VRRPv3 messages, in seconds;
Checksum：The checksum, taking account of the whole VRRPv3 message and an IPv6 pseudo head
(please refer to RFC2460 for details);
IPv6 Address(es)：one or more IPv6 addresses related to the virtual router, the number of which is the
same with ”Count IPv6 Addr”, and the first one of which should be the virtual IPv6
address of the virtual router.
Figure
65-1 VRRPv3 message