Configuring Unidirectional Ethernet

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Noteblank.gif Unidirectional Ethernet is not supported on the following: Catalyst 4900M, Catalyst 4948E, Supervisor Engine 6-E, Supervisor Engine 6L-E, Supervisor Engine 7-E, and Supervisor Engine 7L-E uplinks.

This chapter describes how to configure Unidirectional Ethernet on the Catalyst 4500 series switch and contains these sections:

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Noteblank.gif For complete syntax and usage information for the switch commands used in this chapter, see the
Cisco IOS Command Reference Guides for the Catalyst 4500 Series Switch.

If a command is not in the Cisco Catalyst 4500 Series Switch Command Reference , you can locate it in the Cisco IOS Master Command List, All Releases.

About Unidirectional Ethernet

You can set stubless Gigabit Ethernet ports to unidirectionally transmit or receive traffic. Unidirectional Ethernet uses only one strand of fiber for either transmitting or receiving one-way traffic for the Gigabit Ethernet Port, instead of two strands of fiber for a full-duplex Gigabit Ethernet Port. Configuring your Gigabit Ethernet Port either to transmit or receive traffic effectively doubles the amount of traffic capabilities for applications, such as video streaming, where most traffic is sent as unacknowledged unidirectional video broadcast streams.

Configuring Unidirectional Ethernet

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Noteblank.gif You must configure Unidirectional Ethernet on the non-blocking Gigabit Ethernet Port, which automatically disables UDLD on the port.

To enable Unidirectional Ethernet, perform this task:

 

Command
Purpose

Step 1
Switch(config)# interface { vlan vlan_ID | { fastethernet | gigabitethernet | tengigabitethernet } slot/interface | Port-channel number }

Selects the interface to configure.

Step 2
Switch(config-if)# [ no ] unidirectional { send-only | receive-only }

Enables Unidirectional Ethernet.

Use the no keyword to disable Unidirectional Ethernet.

Step 3
Switch(config-if)# end

Exits configuration mode.

Step 4
Switch# show interface { vlan vlan_ID | { fastethernet | gigabitethernet | tengigabitethernet } slot/interface } unidirectional

Verifies the configuration.

This example shows how to set Gigabit Ethernet interface 1/1 to unidirectionally send traffic:

Switch# configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Switch(config)# interface gigabitethernet 1/1
Switch(config-if)# unidirectional send-only
Switch(config-if)# end
 
Warning!
 
Enable l2 port unidirectional mode will automatically disable port udld.
You must manually ensure that the unidirectional link does not create
a spanning tree loop in the network.
 
Enable l3 port unidirectional mode will automatically disable ip routing
on the port. You must manually configure static ip route and arp entry
in order to route ip traffic.
 

This example shows how to set Gigabit Ethernet interface 1/1 to receive traffic unidirectionally:

Switch# configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Switch(config)# interface gigabitethernet 1/1
Switch(config-if)# unidirectional receive-only
Switch(config-if)# end
 
Warning!
 
Enable l2 port unidirectional mode will automatically disable port udld.
You must manually ensure that the unidirectional link does not create
a spanning tree loop in the network.
 
Enable l3 port unidirectional mode will automatically disable ip routing
on the port. You must manually configure static ip route and arp entry
in order to route ip traffic.
 

This example shows how to verify the configuration:

Switch> show interface gigabitethernet 1/1 unidirectional
show interface gigabitethernet 1/1 unidirectional
Unidirectional configuration mode: send only
CDP neighbor unidirectional configuration mode: receive only
 

This example shows how to disable Unidirectional Ethernet on Gigabit Ethernet interface 1/1:

Switch# configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Switch(config)# interface gigabitethernet 1/1
Switch(config-if)# no unidirectional
Switch(config-if)# end
 

This example shows the result of entering the show interface command for a port that does not support Unidirectional Ethernet:

Switch# show interface f6/1 unidirectional
Unidirectional Ethernet is not supported on FastEthernet6/1