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Cisco ME 3400 Ethernet Access Switch Software Configuration Guide
OL-9639-07
Chapter 9 Configuring Interfaces
Configuring the System MTU
To remove an IP address from an interface, use the no ip address interface configuration command.
This example shows how to configure a port as a routed port and to assign it an IP address:
Switch# configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Switch(config)# interface gigabitethernet0/2
Switch(config-if)# no switchport
Switch(config-if)# ip address 192.20.135.21 255.255.255.0
Configuring the System MTU
The default maximum transmission unit (MTU) size for frames received and sent on all interfaces on the
switch is 1500 bytes. You can increase the MTU size for all interfaces operating at 10 or 100 Mbps by
using the system mtu global configuration command. You can increase the MTU size to support jumbo
frames on all Gigabit Ethernet interfaces by using the system mtu jumbo global configuration
command. You can change the MTU size for routed ports by using the system mtu routing global
configuration command.
Note You cannot configure a routing MTU size that exceeds the system MTU size. If you change the system
MTU size to a value smaller than the currently configured routing MTU size, the configuration change
is accepted, but not applied until the next switch reset. When the configuration change takes effect, the
routing MTU size automatically defaults to the new system MTU size.
Gigabit Ethernet ports are not affected by the system mtu command. Fast Ethernet ports are not affected
by the system mtu jumbo command because jumbo frames are not supported on 10/100 interfaces,
including 100BASE-FX and 100BASE-BX SFP modules. If you do not configure the system mtu jumbo
command, the setting of the system mtu command applies to all Gigabit Ethernet interfaces.
You cannot set the MTU size for an individual interface; you set it for all 10/100 or all Gigabit Ethernet
interfaces on the switch. When you change the system MTU size, you must reset the switch before the
new configuration takes effect. The system mtu routing command does not require a switch reset to take
effect.
Note The system MTU setting is saved in the switch environmental variable in NVRAM and becomes
effective when the switch reloads. The MTU settings you enter with the system mtu and system mtu
jumbo commands are not saved in the switch IOS configuration file, even if you enter the copy
running-config startup-config privileged EXEC command. Therefore, if you use TFTP to configure a
new switch by using a backup configuration file and want the system MTU to be other than the default,
you must explicitly configure the system mtu and system mtu jumbo settings on the new switch and
then reload the switch.
Step 8
show interfaces [interface-id]
show ip interface [interface-id]
show running-config interface [interface-id]
Verify the configuration.
Step 9
copy running-config startup-config (Optional) Save your entries in the configuration file.
Command Purpose
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