- Preface
- Configuring Interface Characteristics
- Configuring Auto-MDIX
- Configuring Ethernet Management Port
- Checking Port Status and Connectivity
- Configuring LLDP, LLDP-MED, and Wired Location Service
- Configuring System MTU
- Configuring Per-Port MTU
- Configuring Internal Power Supplies
- Configuring the Cisco Expandable Power System 2200
- Configuring EEE
- Configuring Power over Ethernet
- Configuring Perpetual PoE and Fast POE
- Configuring 2-event Classification
- Configuring Auto SmartPorts
- Configuring COAP Proxy Server
- Configuring USB 3.0 SSD
- Configuring an External USB Bluetooth Dongle
- Troubleshooting Interface and Hardware Components
Configuring System MTU
Information About the MTU
The default maximum transmission unit (MTU) size for payload received in Ethernet frame and sent on all device interfaces is 1500 bytes. The maximum value of System MTU is 9198 bytes.
System MTU Value Application
This table shows how the MTU values are applied.
|
Configuration |
system mtu command |
ip mtu command |
ipv6 mtu command |
||||
|---|---|---|---|---|---|---|---|
|
Standalone switch or switch stack |
You can enter the system mtu command on a switch or switch stack. It affects all ports. The range is from 1500 to 9198 bytes. |
Use the ip mtu bytes command. The range is from 832 up to 1500 bytes.
|
Use the ipv6 mtu bytes command. The range is from 1280 to the system jumbo MTU value (in bytes).
|
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 value. For more information about setting the MTU sizes, see the system mtu global configuration command in the command reference for this release.
Beginning from Cisco IOS XE Amsterdam 17.3.x, the minimum IPv6 system MTU is fixed at 1280 as per RFC 8200.
How to Configure MTU
The following tasks describe how you can configure MTU.
Configuring the System MTU
Follow these steps to change the MTU size for switched packets:
Procedure
| Command or Action | Purpose | |
|---|---|---|
|
Step 1 |
enable Example: |
Enables privileged EXEC mode. Enter your password, if prompted. |
|
Step 2 |
configure terminal Example: |
Enters global configuration mode. |
|
Step 3 |
system mtu bytes Example: |
(Optional) Changes the MTU size for all Gigabit Ethernet and 10-Gigabit Ethernet interfaces. |
|
Step 4 |
end Example: |
Enters global configuration mode, and returns to privileged EXEC mode. |
|
Step 5 |
copy running-config startup-config Example: |
Saves your entries in the configuration file. |
|
Step 6 |
show system mtu Example: |
Verifies your settings. |
Configuring Protocol-Specific MTU
To override system MTU values on routed interfaces, configure protocol-specific MTU under each routed interface. To change the MTU size for routed ports, perform this procedure.
Procedure
| Command or Action | Purpose | |
|---|---|---|
|
Step 1 |
configure terminal Example: |
Enters global configuration mode. |
|
Step 2 |
interface interface Example: |
Enters interface configuration mode. |
|
Step 3 |
ip mtu bytes Example: |
Changes the IPv4 MTU size |
|
Step 4 |
ipv6 mtu bytes Example: |
(Optional) Changes the IPv6 MTU size. |
|
Step 5 |
end Example: |
Exits interface configuration mode, and returns to privileged EXEC mode. |
|
Step 6 |
copy running-config startup-config Example: |
Saves your entries in the configuration file. |
|
Step 7 |
show system mtu Example: |
Verifies your settings. |
Configuration Examples for System MTU
Example: Configuring Protocol-Specific MTU
This example shows how you can configure protocol-specific MTU:
Device# configure terminal
Device(config)# interface gigabitethernet 0/1
Device(config-if)# ip mtu 900
Device(config-if)# ipv6 mtu 1286
Device(config-if)# end
Example: Configuring the System MTU
This example shows how you can configure the system MTU:
Device# configure terminal
Device(config)# system mtu 1600
Device(config)# exit
Additional References for System MTU
Related Documents
| Related Topic | Document Title |
|---|---|
|
For complete syntax and usage information for the commands used in this chapter. |
See the Interface and Hardware Commands section in the Command Reference (Catalyst 9300 Series Switches) |
Standards and RFCs
| Standard/RFC | Title |
|---|---|
| RFC 8200 |
Internet Protocol, Version 6 (IPv6) Specification |
Feature History for System MTU
This table provides release and related information for features explained in this module.
These features are available on all releases subsequent to the one they were introduced in, unless noted otherwise.
|
Release |
Feature |
Feature Information |
|---|---|---|
|
Cisco IOS XE Everest 16.5.1a |
System MTU |
System MTU defines the maximum transmission unit size for frames transmitted on all interfaces of a switch. |
Use Cisco Feature Navigator to find information about platform and software image support. To access Cisco Feature Navigator, go to https://cfnng.cisco.com/.
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