System Mtu - Cisco Catalyst 2960 Command Reference Manual

system mtu

system mtu
Use the system mtu global configuration command to set the maximum packet size or maximum
transmission unit (MTU) size for Gigabit Ethernet ports or for Fast Ethernet (10/100) ports. Use the no
form of this command to restore the global MTU value to its default value.
Syntax Description
bytes
jumbo bytes
Defaults
The default MTU size for all ports is 1500 bytes.
Command Modes Global configuration
Command History Release
12.2(25)FX
Usage Guidelines When you use this command to change the system MTU or jumbo MTU size, you must reset the switch
before the new configuration takes effect.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.
Gigabit Ethernet ports operating at 1000 Mb/s are not affected by the system mtu command, and
10/100-Mb/s ports are not affected by the system mtu jumbo command.
If you enter a value that is outside the range for the specific type of switch, the value is not accepted.
The switch does not support setting the MTU on a per-interface basis.
Note
The size of frames that can be received by the switch CPU is limited to 1998 bytes, regardless of the
value entered with the system mtu command. Although forwarded or routed frames are usually not
received by the CPU, some packets (for example, control traffic, SNMP, Telnet, and routing protocols)
are sent to the CPU.
Catalyst 2960 Switch Command Reference
2-569
system mtu {bytes | jumbo bytes}
no system mtu
Set the system MTU for ports that are set to 10 or 100 Mb/s. The range
is 1500 to 1998 bytes. This is the maximum MTU received at 10/100-Mb/s
Ethernet switch ports.
Set the system jumbo MTU for Gigabit Ethernet ports operating at 1000
Mb/s or greater. The range is 1500 to 9000 bytes. This is the maximum MTU
received at the physical port for Gigabit Ethernet ports.
Modification
This command was introduced.
Chapter 2 Catalyst 2960 Switch Cisco IOS Commands
OL-8604-04