Cisco Catalyst 2960: Настройка максимального размера передачи (MTU)

System MTU Value Application

Configuring System MTU Information About the MTU, on page 1 How to Configure MTU , on page 2 Configuration Examples for System MTU, on page 3 Additional References for System MTU, on page 4 Feature History for System MTU, on page 4 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. Table 1: MTU Values 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. To view the correct MTU value for interfaces, use the show ip mtu command which includes MTU values of logical loopback interfaces also. Configuring System MTU 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. Note The IP MTU value is the applied value, not the configured value. Use the ipv6 mtu bytes command.

The range is from 1280 to the system jumbo MTU value (in bytes). Note The IPv6 MTU value is the applied value, not the configured value. 1

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Configuring Protocol-Specific MTU

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 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. Configuring System MTU How to Configure MTU Command or Action Purpose Step 1 enable Example: Device> enable Enables privileged EXEC mode. Enter your password, if prompted.

Step 2 configure terminal Example: Device# configure terminal Enters global configuration mode. Step 3 system mtu bytes Example: Device(config)# system mtu 1900 (Optional) Changes the MTU size for all Gigabit Ethernet and 10-Gigabit Ethernet interfaces. Step 4 end Example: Device(config)# end Enters global configuration mode, and 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 show system mtu Example: Device# show system mtu Verifies your settings. Configuring System MTU 2

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Example: Configuring Protocol-Specific MTU

Procedure 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 Configuring System MTU Configuration Examples for System MTU Command or Action Purpose Step 1 configure terminal Example: Device# configure terminal Enters global configuration mode. Step 2 interface interface Example: Device(config)# interface gigabitethernet0/0 Enters interface configuration mode. Step 3 ip mtu bytes Example: Device(config-if)# ip mtu 68 Changes the IPv4 MTU size Step 4 ipv6 mtu bytes Example:

Device(config-if)# ipv6 mtu 1280 (Optional) Changes the IPv6 MTU size. Step 5 end Example: Device(config-if)# end Exits interface configuration mode, and returns to privileged EXEC mode. Step 6 copy running-config startup-config Example: Device# copy running-config startup-config Saves your entries in the configuration file. Step 7 show system mtu Example: Device# show system mtu Verifies your settings. Configuring System MTU 3

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Feature History for System MTU

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 Standards and RFCs 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. Use Cisco Feature Navigator to find information about platform and software image support. To access Cisco Feature Navigator, go to https://cfnng.cisco.com/ .

Configuring System MTU Example: Configuring the System MTU 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) Standard/RFC Title RFC 8200 Internet Protocol, Version 6 (IPv6) Specification 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. Configuring System MTU 4

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