Configure Interface Speed and Duplex on Cisco devices

By default, Cisco switches will auto-negotiate the speed and duplex settings. When you connect a device (either a switch, router, or a workstation) to a port on a Cisco switch, the negotiation process will occur and the devices will agree on the transmission parameters. Most of the today’s network adapters support this function.

In this article, you will see how to configure interface speed and duplex in Cisco devices using NCM application's configlets feature. If you don't have NCM installed, please click here to download and install the application.

Steps to configure interface speed through CLI.

  1. Login to the device using SSH / TELNET and go to enable mode.

  2. Execute Show interface command to view the interface configuration
    Router#show interface Fa0/1
    FastEthernet0/1 is up, line protocol is up (connected)
    Hardware is Lance, address is 0009.7c66.6401 (bia 0009.7c66.6401)
    ...
    Half-duplex, 100Mb/s
    ...
    Router#

  3. Go into the config mode.
    Router#configure terminal
    Enter configuration commands, one per line. End with CNTL/Z. 
    Router(config)#

  4. Go into the interface config mode
    Router(config)#interface Fa0/1
    Router(config-if)#

  5. Configure Speed
    Router(config-if)#speed 100
    Router(config-if)#

  6. Configure Duplex
    Router(config-if)#duplex full
    Router(config-if)#

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  8. Exit interface configuration mode
    Router(config-if)#exit
    Router(config)#

  9. Exit Configuration mode
    Router(config)#exit
    Router#

  10. Execute show interface and view the changes
    Router#show interface Fa0/1
    FastEthernet0/1 is up, line protocol is up (connected)
    Hardware is Lance, address is 0009.7c66.6401 (bia 0009.7c66.6401)
    ...
    Full-duplex, 100Mb/s
    ...
    Router#

  11. Copy the running configuration into startup configuration using below command
    Router#write memory
    Building configuration... [OK]
    Router#

Corresponding configlet can be created in NCM application as shown in below screenshot.

Configure Interface Speed and Duplex Cisco

Also you can click the below button to download the Configlet as XML and import it into NCM application using file import option.

Download Configlet XML
SHA256 value
2f30b74e1a3a62583dc35e1081914a8c3eeedac6dc07e1fd862b90231b2bede1
Click to copy SHA256 value
Configlet Name Configure Interface Speed and Duplex Cisco
Description Script execution mode
Execution Mode This configlet is used to configure the interface speed and duplex on multiple cisco devices simultaneously
Configlet Content

show interface $INTERFACE
configure terminal
interface $INTERFACE
speed $SPEED
duplex $DUPLEX
exit
exit
show interface $INTERFACE
write memory