Configuring DLF Forwarding

Information About Destination Lookup Failure Forwarding

When a packet arrives at the device and the device doesn't have an entry for the destination MAC address in its MAC address table, the packet is classified as a Destination Lookup Failure (DLF). The DLF frame is flooded to all the ports except the one from which it was received. A host in the network responds to the frame. A corresponding forwarding MAC address table entry is created for the host.

Unknown packets are classified into unknown unicast packets and unknown multicast packets. Unknown unicast packets are packets that can't find the destination MAC addresses in the MAC table. Unknown multicast packets are packets that can't find the destination MAC addresses of the multicast packets in the multicast MAC table.

You can disable or enable DLF forwarding at a global configuration level or an interface configuration level. DLF Forwarding is enabled by default.

Configuring DLF Forwarding control

You can configure DLF Forwarding at the global or interface configuration levels. The following topics show you how to configure DLF Forwarding control.

Configuring DLF Forwarding in Global Configuration Mode

If you enable DLF forwarding at global configuration level, DLF Forwarding is enabled on egress packets of all ports. DLF forwarding is enabled by default. To disable or enable DLF Forwarding, perform this procedure:

Procedure

  Command or Action Purpose
Step 1

enable

Example:

Device> enable

Enables privileged EXEC mode. Enter your password, if prompted.

Step 2

configure terminal

Example:

Device# configure terminal

Enters global configuration mode.

Step 3

dlf-forward unicast

Example:

Device(config)# dlf-forward unicast

Enables the forwarding function for DLF unicast packets. DLF Forwarding is enabled by default. To disable it, use the no form of the command.

Step 4

dlf-forward multicast

Example:

Device(config)# dlf-forward multicast

Enables the forwarding function for DLF multicast packets. DLF Forwarding is enabled by default. To disable it, use the no form of the command.

Configuring DLF Forwarding in Interface Configuration Mode

If you enable DLF forwarding at interface configuration level, DLF Forwarding will be enabled on egress packets of the specified port. DLF forwarding is enabled by default. To disable or enable DLF Forwarding, perform this procedure:

Procedure

  Command or Action Purpose
Step 1

enable

Example:

Device> enable

Enables privileged EXEC mode. Enter your password, if prompted.

Step 2

configure terminal

Example:

Device# configure terminal

Enters global configuration mode.

Step 3

interface ethernet port-number

Example:

Device(config)# interface ethernet 1/4

Enters interface configuration mode.
Step 4

dlf-forward unicast

Example:

Device(config-if)# dlf-forward unicast

Enables the forwarding function for DLF unicast packets. DLF Forwarding is enabled by default. To disable it use the no form of the command.

Step 5

dlf-forward multicast

Example:

Device(config-if)# dlf-forward multicast

Enables the forwarding function for DLF multicast packets. DLF Forwarding is enabled by default. To disable it use the no form of the command.

Step 6

end

Example:

Device(config-if)# end

Returns to privileged EXEC mode.
Step 7

show dlf-forward interface ethernet port-number

Example:

Device# show dlf-forward interface ethernet 1/4

Displays the DLF Forwarding configuration for the port.

Example: Configuring DLF Forwarding

The following example shows how to disable DLF forwarding for unicast packets on a port:

Device> enable
Device# configure terminal
Device(config)# interface ethernet 1/2
Device(config-if)# no dlf-forward unicast

The following example shows how to display the DLF Forwarding configuration on Port 2:

Device(config)# show dlf-forward interface ethernet 1/2
Forwarding unknown unicast packets global status:  enable
Forwarding unknown multicast packets global status:  enable
Port        Forwarding Unknown Unicast      Forwarding Unknown Multicast
e1/1      disable                         enable