Description

Passive ARP learning enables the ARP cache in the backup router to hold approximately the same contents as the ARP cache in the primary router, thus preventing the problem of learning ARP entries in a burst.

By default, the backup VRRP router will drop ARP requests for VRRP-IP to VRRP-MAC address.

After enabling passive ARP learning on backup VRRP router, the backup VRRP router will add it to its ARP cache/table, when the ARP request comes in. When the primary VRRP router fails the backup device will have ARP entries of the hosts and it need not to learn them again.

The above information is from the tech document, Configuring Passive ARP Learning for Backup VRRP Routers .

Solution

To enable Passive ARP Learning, include the passive-learning statement under [edit system arp] hierarchy level:

[edit system arp]
  passive-learning;

Topology for the following sample configurations:


alt


Configuration on backup VRRP router:

root@SWITCH-2# Set system arp passive-learning

In the above topology, switch-1 is the VRRP primary and switch-2 is VRRP backup.

alt


Note : Juniper recommends setting passive learning on both the backup and primary VRRP routers.

Related Information