Nokia IPSO 4.0 manual Selecting Configuration Parameters, Priority

Use this method only if you do not have an extra IP address to use for monitored-circuit VRRP. For more information see “Configuring VRRPv2”.

Selecting Configuration Parameters

Before you begin, plan your implementation by deciding how you want to set the following configuration parameters.

„Priority

„Hello Interval

„Authentication

„Priority Delta

„Backup Address

„VMAC Mode

Priority

The priority value determines which router takes over in the event of a failure; the router with the higher priority becomes the new master. The range of values for priority is 1 to 254. The default setting is 100.

Note

In Nokia’s monitored-circuit VRRP, the master is defined as the router with the highest priority setting, although RFC 3768 specifies that the master must have a priority setting of 255.

If two platforms have equivalent priorities, the platform that comes online and starts broadcasting VRRP advertisements first becomes the master. If there is a tie, the platform with the higher IP address is selected.

To prevent the unlikely event that the tie-breaking algorithm selects one platform as the master for the external network and another as the master router for the internal network, you should make all interfaces on one platform numerically greater than the interfaces on the peer. For example, Platform A should be the .1 host and Platform B should be the .2 host on all connected interfaces.

You should set the priority to 254 for least the master platform in each VRID to provide a faster transition in the event of a failure. Using higher values can decrease the time it takes for a backup router to take over for a failed router by close to one second.

Note

Setting a higher priority shortens the transition time because the time interval for a backup to declare the master down is calculated as

Master_Down_Interval = (3 * Hello_interval) + Skew_time; and the skew time (seconds by

Nokia Network Voyager for IPSO 4.0 Reference Guide 187