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Configuring Unknown Unicast Forwarding

 

Unknown unicast packets have unknown destination MAC addresses. By default, these packets are flooded out all the ports in the VLAN, which can trigger a traffic storm and cause security issues and performance degradation.

To prevent storms, configure a VLAN to forward unknown unicast traffic to a trunk port. The destination MAC address can be learned from the trunk port and added to the Ethernet switching table. You can configure different VLANs to forward unknown unicast traffic to different trunk interfaces or use one trunk interface for multiple VLANs.

To configure unknown unicast forwarding options using the CLI:

Note

Before you can configure unknown unicast forwarding within a VLAN, you must first configure that VLAN.

  1. Configure unknown unicast forwarding for a specific VLAN:
    [edit ethernet-switching-options]

    user@switch# set unknown-unicast-forwarding vlan VLAN-name
  2. Specify the trunk interface to which unknown unicast traffic will be forwarded:
    [edit ethernet-switching-options ]

    user@switch# set unknown-unicast-forwarding vlan VLAN-name interface (Unknown Unicast Forwarding) interface-name