Configuring System MTU
This module describes how to configure the Maximum Transmission Unit for a system on Catalyst 3650 Series Switches and Catalyst 3850 Series Switches.
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.
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Information about the MTU
The default maximum transmission unit (MTU) size for frames received and sent on all switch interfaces is 1500 bytes.
Restrictions for System MTU
When configuring the system MTU values, follow these guidelines:
-
The switch does not support the MTU on a per-interface basis.
-
If you enter the system mtu bytes global configuration command, the command does not take effect on the switch. This command only affects the system MTU size on Fast Ethernet switch ports.
System MTU Value Application
In a switch stack, the MTU values applied to member switches depends upon the stack configuration. The following stack configurations are supported:
The upper limit of the IP or IPv6 MTU value is based on the switch or switch stack configuration and refers to the currently applied system MTU or the system jumbo MTU value. For more information about setting the MTU sizes, see the system mtu global configuration command in the command reference for this release.
Configuring the System MTU
Configuring the System MTU
Procedure
| Command or Action | Purpose | |
|---|---|---|
| Step 1 |
enable Example: |
|
| Step 2 |
configure terminal Example: |
Enters global configuration mode. |
| Step 3 |
system mtu bytes Example: |
|
| Step 4 |
exit Example: |
Exits global configuration mode and returns to privileged EXEC mode. |
| Step 5 |
show system mtu Example: |
Displays the configured global MTU size. |
Configuring Protocol-Specific MTU
When system MTU changes, the range for the ip mtu command for interface also changes.
Procedure
| Command or Action | Purpose | |
|---|---|---|
| Step 1 |
enable Example: |
|
| Step 2 |
configure terminal Example: |
Enters global configuration mode. |
| Step 3 |
interface type number Example: |
Configures an interface and enters interface configuration mode. |
| Step 4 |
ip mtu bytes Example: |
|
| Step 5 |
ipv6 mtu bytes Example: |
|
| Step 6 |
end Example: |
Exits interface configuration mode and returns to privileged EXEC mode. |
| Step 7 |
show system mtu Example: |
Displays the configured global MTU size. |
Configuration Examples for System MTU
Example: Configuring the System MTU
Switch# configure terminal
Switch(config)# system mtu 1600
Switch(config)# exit
Example: Configuring Protocol-Specific MTU
Switch# configure terminal
Switch(config)# interface gigabitethernet 0/0
Switch(config-if)# ip mtu 900
Switch(config-if)# ipv6 mtu 1286
Switch(config-if)# end
Additional References for System MTU
Error Message Decoder
| Description | Link |
|---|---|
|
To help you research and resolve system error messages in this release, use the Error Message Decoder tool. |
https://www.cisco.com/cgi-bin/Support/Errordecoder/index.cgi |
MIBs
| MIB | MIBs Link |
|---|---|
|
All supported MIBs for this release. |
To locate and download MIBs for selected platforms, Cisco IOS releases, and feature sets, use Cisco MIB Locator found at the following URL: |
Technical Assistance
| Description | Link |
|---|---|
|
The Cisco Support website provides extensive online resources, including documentation and tools for troubleshooting and resolving technical issues with Cisco products and technologies. To receive security and technical information about your products, you can subscribe to various services, such as the Product Alert Tool (accessed from Field Notices), the Cisco Technical Services Newsletter, and Really Simple Syndication (RSS) Feeds. Access to most tools on the Cisco Support website requires a Cisco.com user ID and password. |
Feature Information for System MTU
|
Release |
Modification |
|---|---|
|
Cisco IOS XE 3.2SECisco IOS XE 3.3SE Cisco IOS XE 3.3SE |
This feature was introduced. |
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