HP 3500YL - Manual (Page 356)

Virtual Router Redundancy Protocol (VRRP)
Dynamically Changing the Priority of the VR
Dynamically Changing the Priority of the
VR
The dynamic priority change feature provides the ability to dynamically
change the priority of the virtual router (VR) when certain events occur. The
Backup VR releases virtual IP address control by reducing its priority when
tracked entities such as ports, trunks, or VLANs go down. You can also force
the Backup to take ownership of the VR if you have previously caused it to
release control.
In normal VRRP operation, one router (Router-1) is in the Master state and
one router (Router-2) is in the Backup state. Router-1 provides the default
gateway for the host. If Router-1 goes down for any reason, the Backup router,
Router-2, provides the default gateway for the host.
Router 1 Configuration
VRID: 1
Status: Master
Virtual IP Addr: 10.10.10.1
MAC Addr: 00-00-5E-00-01-01
Priority: 150
Router-1
VLAN VID: 22
IP: 10.10.10.21
Router-2
VLAN VID: 22
IP: 10.10.10.23
Switch
VLAN VID: 22
Intranet
Host “A”
Router 2 Configuration
VRID: 1
Status: Backup
Virtual IP Addr: 10.10.10.1
MAC Addr: 00-00-5E-00-01-01
Priority: 100
VR 1
10.10.10.1
(Virtual IP Address)
Figure 6-8. Example VRRP Configuration
If all the tracked entities configured on Router-1 go down, Router-1 begins
sending advertisements with a priority of zero. This causes Router-2 to take
control of the virtual IP.
Any applications or routing protocols such as RIP or OSPF on Router-1 that
were using its IP address are no longer able to use that IP interface. Router-1
does not respond to any ARP requests for that IP address. Router-2 takes
control of the IP address and responds to ARP requests for it with the virtual
MAC address that corresponds to VRID-1.
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