ip mtu

Changes the Maximum Transmission Unit (MTU) for a specific interface.
Syntax
ip mtu value
no ip mtu value
Command Default

1500 bytes for Ethernet II encapsulation and 1492 bytes for SNAP encapsulation. When jumbo mode is enabled, the default is 9216.

Parameters
value
Specifies the MTU. Ethernet II packets can hold IP packets from 576 through 1500 bytes long. If jumbo mode is enabled, Ethernet II packets can hold IP packets up to 10,178 bytes long. Ethernet SNAP packets can hold IP packets from 576 through 1492 bytes long. If jumbo mode is enabled, SNAP packets can hold IP packets up to 10,174 bytes long. The default MTU for Ethernet II packets is 1500. The default MTU for SNAP packets is 1492.
For ICX 7850 devices, the maximum jumbo frame size supported is 9380. When jumbo mode is enabled, the maximum ethernet MTU size is 9358 bytes.
Modes

Interface subtype configuration mode

Usage Guidelines

If you set the MTU of a port to a value lower than the global MTU and from 576 through 1499, the port fragments the packets. However, if the port MTU is exactly 1500 and this is larger than the global MTU, the port drops the packets. The minimum IPv4 MTU values for both physical and virtual interfaces are 1280.

This command is applicable on physical ports with an IP address configured, or on Virtual Ethernet (VE) interfaces.

The configuration takes effect immediately. Use the write memory command to save the change across reboots.

The no form of the command resets the default MTU values.

Examples

The following example configures the IP MTU as 1300 for an Ethernet interface. 

device# configure terminal
device(config)# interface ethernet 1/1/5
device(config-if-e1000-1/1/5)# ip mtu 1300
device(config-if-e1000-1/1/5)# write memory
device(config-if-e1000-1/1/5)# end

The following example configures the IP MTU as 1300 for a VE interface. 

device# configure terminal
device(config)#interface ve 1
device(config-vif-1)# ip mtu 1300
INFO: IPv6 MTU also changed to 1300 as part of IP MTU config
device(config-vif-1)# write memory
device(config-vif-1)# end
Parent topic: Commands I