Principles Of Vrrp; Vrrp Tracking - HP 6125G Configuration Manual

Count IP Addrs/Count IPv6 Addrs—Number of virtual IPv4 or IPv6 addresses for the VRRP group.
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A VRRP group can have multiple virtual IPv4 or IPv6 addresses.
Auth Type—Authentication type. 0 means no authentication, 1 means simple text authentication,
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and 2 means MD5 authentication. VRRPv3 does not support MD5 authentication.
Adver Int—Interval for sending advertisement packets. For VRRPv2, the interval is in seconds and
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defaults to 1. For VRRPv3, the interval is in centiseconds and defaults to 100.
Checksum—16-bit checksum for validating the data in VRRP packets.
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• 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.
Authentication Data—Authentication key. This field is used only for simple authentication and is 0
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for any other authentication modes.

Principles of VRRP

• Routers in a VRRP group determine their roles by priority. The router with the highest priority is the
master, and the others are the backups. The master periodically sends VRRP advertisements to notify
the backups that it is operating properly, and each of the backups starts a timer to wait for
advertisements from the master.
In preemptive mode, when a backup receives a VRRP advertisement, it compares the priority in the
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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.
In non-preemptive mode, a router in the VRRP group remains as a master or backup as long as the
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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.
If the timer of a backup expires but the backup still does not receive any VRRP advertisement, it
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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.
The VRRP group configuration might be different on routers, and network problems might exist, so
multiple master routers might exist in one VRRP group. These master routers will elect one master
according to their priorities and IP addresses. The router with the highest priority wins the election. If a tie
exists in the priority, the router with the highest IP address wins.
After a backup router receives an advertisement, it compares its priority against that carried in the
advertisement. If its priority is higher than that carried in the advertisement, it takes over the master.

VRRP tracking

To enable the VRRP tracking function, configure the routers in the VRRP group to operate in preemptive
mode first, so that only the router with the highest priority can always operate as the master for packet
forwarding.
Tracking a specified interface
The interface tracking function expands the backup functionality of VRRP. It provides backup not only
when the interface to which a VRRP group is assigned fails but also when other interfaces (such as uplink
interfaces) on the router become unavailable.
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