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VRRP (Virtual Router Redundancy Protocol) Configuration
Issue 1 July 2006 179
● By the end of the routers configuration, and when the network is up, the main router for
each virtual router will be elected according to this order of preference:
- The virtual router IP address is also the router's interface IP address
- It has the highest priority (you can configure this parameter)
- It has the highest IP address if the previous cases do not apply
● The virtual router IP address needs to be configured as Default Gateway on the stations
● The MAC which will be advertised by the Main router as a response to the stations ARP
requests, will be a 6 bytes Virtual MAC address in the format 00.00.5E.00.01.VRID.
● In the meantime, the redundant router will use a VRRP polling protocol to check the Main
router integrity in one second intervals (default). Otherwise it will be idle.
● If the Main router fails, a redundant router that has not received a response from four
consecutive polling requests (default) will take over and start to advertise the same Virtual
MAC for the ARP requests. Therefore the stations will not 'sense' any change neither in
the configured DG nor in the MAC level.
● VRRP has no provisions for routing data base synchronization among the redundant
routers. You need to perform this manually.
Case #2
● One router is Main on one IP subnet (e.g. 20.20.20.0) and redundant on another (e.g.
30.30.30.0)
● In this case each IP subnet must be in different VRID (e.g. 1 & 2)
● The above detailed information is valid for each router in its Main/Redundant roles.
VRRP CLI Commands
In order to... Use the following command...
Enable or disable VRRP routing
globally
router vrrp
Create or delete a virtual router
on the interface
ip vrrp
Assign or remove an IP address
to the virtual router
ip vrrp address
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