Configuring System MTU

Finding Feature Information

Your software release may not support all the features documented in this module. For the latest caveats and feature information, see Bug Search Tool and the release notes for your platform and software release. To find information about the features documented in this module, and to see a list of the releases in which each feature is supported, see the feature information table at the end of this module.

Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn. An account on Cisco.com is not required.

Information About the MTU

The default maximum transmission unit (MTU) size for frames received and transmitted on all interfaces is 1500 bytes.

How to Configure MTU

Configuring the System MTU

Beginning in privileged EXEC mode, follow these steps to change the MTU size for all 10/100 or Gigabit Ethernet interfaces:

SUMMARY STEPS

  1. configure terminal
  2. system mtu bytes
  3. system mtu jumbo
  4. end
  5. copy running-config startup-config
  6. do show system mtu

DETAILED STEPS

  Command or Action Purpose
Step 1

configure terminal

Example:

Device# configure terminal

Enters global configuration mode.

Step 2

system mtu bytes

Example:

Device(config)# system mtu 1500

(Optional) Change the MTU size for all interfaces on the switch stack that are operating at 10 or 100 Mb/s.

Enter 1500, 2026 or jumbo to specify the MTU size. The MTU value of jumbo is 10218.

Step 3

system mtu jumbo

Example:

Device(config)# system mtu jumbo

(Optional) Changes the MTU size for all Gigabit Ethernet interfaces on the switch or the switch stack.

Enter 1500, 2026 or jumbo to specify the MTU size. The MTU value of jumbo is 10218.

Step 4

end

Example:

Device(config)#  end

Returns to privileged EXEC mode.

Step 5

copy running-config startup-config

Example:

Device# copy running-config startup-config

Saves your entries in the configuration file.

Step 6

do show system mtu

Example:

Device# do show system mtu

Configuration Examples for System MTU

This example shows how to set the maximum packet size for a Gigabit Ethernet port to 1500 bytes: 


Device(config)# system mtu 1500system mtu 1900

Device(config)# exit

This is an example of output from the show system mtu command: 


Device# show system mtu
System MTU size is 1500 bytes.