Example network
each virtual IP address. The end devices in each VLAN will be configured to use that VLAN's
virtual IP address as the default gateway IP address when sending traffic from their local
network.
Any end device that wants to send traffic from the local network will ARP for the Layer 2
address of the default gateway. The VRRP master router for the VLAN will respond, sending
its VRRP virtual MAC address. Once a response is received from the current master in the
virtual router, the end device will send traffic destined for outside the local network to the
VRRP virtual MAC address.
Core switch 1 is the VRRP master router for all VLANs, and therefore we configure a higher
VRRP priority value on it than on its partner switch core 2. Hence core 1 processes any
traffic that has a Layer 2 destination MAC address equal to the virtual MAC address owned
by the VRRP master router in any VLAN.
The backup VRRP switch, core 2, shadows the setup of core 1 and is also configured for the
same VLANs.
If core 1 fails completely, core 2 will stop receiving VRRP messages from core 1. Core 2 will
assume the new forwarding responsibility for all of the VLANs.
If core 1 service is restored, then VRRP message exchanges between core 1 and core 2 will
restart, and core 1 will return to the Master state and assume responsibility for all forwarding
of traffic sent to the VRRP virtual address. This is the default behaviour and is called
pre-empting—allowing the VRRP device with the highest priority to assume the master role
from another device that is currently acting as the master but that has a lower priority value.
Monitored
Depending on your server farm configuration, you may need to monitor VLANs on the
interfaces
server side of the core switches. If one of the links from the current VRRP master to the
server farm goes down, that switch may need to stop being the master.
To configure this, add the following command to the configuration:
add vrrp=<id> monitoredinterface=<vlan>
For more information, see the Software Reference and How to Configure Microsoft Windows
2003 Network Load Balancing Clustering with Allied Telesis Switches. This How To Note is
available from www.alliedtelesis.com/resources/literature/howto.aspx.
Page 3 | AlliedWare™ OS How To Note: VRRP
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