Configuring System MTU

Information About the MTU

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

You can change the MTU size to support switched jumbo frames on all Gigabit Ethernet and 10-Gigabit Ethernet interfaces and to support routed frames on all routed ports.

The default maximum transmission unit (MTU) size for frames received and transmitted on all interfaces is 1500 bytes. You can increase the MTU size to support jumbo frames on all Gigabit Ethernet interfaces by using the system mtu jumbo global configuration command.

Gigabit Ethernet ports are not affected by the system mtu command; 10/100 ports are not affected by the system mtu jumbo command. If you do not configure the system mtu jumbo command, the setting of the system mtu command applies to all Gigabit Ethernet interfaces.

How to Configure System MTU Sizes

Configuring the System MTU

Beginning in privileged EXEC mode, follow these steps to change the MTU size.

Procedure

  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. routing sets the routing MTU for the system.

Step 3

end

Example:

Device(config)#  end

Returns to privileged EXEC mode.

Step 4

copy running-config startup-config

Example:

Device# copy running-config startup-config

Saves your entries in the configuration file.

Step 5

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 port to 1500 bytes: 


Device(config)# system mtu 1500

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


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

Feature Information for MTU

The following table provides release information about the feature or features described in this module. This table lists only the software release that introduced support for a given feature in a given software release train. Unless noted otherwise, subsequent releases of that software release train also support that feature.

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

Feature Name

Releases

Feature Information

MTU

Cisco IOS Release 15.2(5)E

This feature was introduced.