Configuring The Advertisement Interval; Configuring Virtual Router Priority - Alcatel OmniSwitch 6624 Network Configuration Manual

Configuring VRRP

Configuring the Advertisement Interval

The advertisement interval is configurable, but all virtual routers with the same VRID should be config-
ured with the same value. Mismatched values will create network problems.
If you change the advertisement interval on the master router when VRRP is already running or if the
advertisement interval is set differently for a master router and a backup router, VRRP packets may be
dropped because the newly configured interval does not match the interval indicated in the packet. The
backup router will then take over and send a gratuitous ARP
and the virtual router MAC address. In addition to creating duplicate IP/MAC address messages, both
routers will begin forwarding packets sent to the virtual router MAC address. This will result in forward-
ing duplicate packets.
To avoid duplicate addresses and packets, make sure the advertisement interval is configured the same on
both the master and the backup router.
For more information about VRRP and ARP requests, see
To configure the advertisement interval, use the
-> vrrp 6 4 disable
-> vrrp 6 4 interval 5
In this example, virtual router 6 is disabled. (If you are modifying an existing virtual router, the virtual
router must be disabled before it may be modified.) The vrrp command is then used to set the advertising
interval for virtual router 6 to 5 seconds.

Configuring Virtual Router Priority

VRRP functions with one master virtual router and at least one backup virtual router. A priority value
determines how backup routers will be selected to take over for the master router if it becomes unavail-
able.
Priority values range from 1 to 254. A value of 255 indicates that the virtual router owns the IP address;
that is, the router contains the real physical interface to which the IP address is assigned. The default prior-
ity value is 100; however the switch sets this value to 255 if it detects that this router is the IP address
owner. The value cannot be set to 255 if the router is not the IP address owner. The IP address owner will
always be the master router if it is available.
If more than one backup router is configured, their priority values may be configured with different
values, so that the backup with the higher value will take over for the master. The priority parameter may
be used to control the order in which backup routers will take over for the master. If priority values are the
same, any backup will take over for master.
Note that the switch sets the priority value to zero in the last VRRP advertisement packet before a master
router is disabled (see
Also, if a router is the IP address owner and the priority value is not set to 255, the switch will set its prior-
ity to 255 when the router is enabled.
To set the priority, use the
-> vrrp 6 4 disable
-> vrrp 6 4 priority 50
OmniSwitch 6624/6648 Network Configuration Guide
"Enabling/Disabling a Virtual Router" on page
vrrp command with the priority keyword and the desired value. For example:
which includes the virtual router IP address
,
"ARP Requests" on page
vrrp command with the interval keyword. For example:
16-11).
April 2004
Configuration Overview
16-6.
page 16-9