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Catalyst 3750-X and 3560-X Switch Software Configuration Guide
OL-21521-01
Chapter 13 Configuring Interface Characteristics
Configuring the System MTU
• You can enter the system mtu bytes global configuration command on a Catalyst 3750-X switch,
but the command does not take effect on the switch. This command only affects the system MTU
size on Fast Ethernet ports on Catalyst 3750 members in a mixed hardware switch stack. In this
stack, you can use the system mtu bytes global configuration command on a Catalyst 3750-X
member to configure the system MTU size on a Catalyst 3750 member.
• The system mtu, system mtu jumbo, and system mtu routing global configuration commands do
not take effect in these cases:
–
When you enter the system mtu command on a Catalyst 3750-X or 3560-X switch
–
In a mixed stack when you enter the system mtu jumbo command for the Fast Ethernet ports
on a Catalyst 3750 member
–
When you enter the system mtu routing command on a switch on which only Layer 2 ports are
configured
Note This command is not supported on switches running the LAN base feature set.
• When you use the system mtu bytes or system mtu jumbo bytes command to change the system
MTU or system jumbo 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.
The system MTU setting is saved in the switch environmental variable in NVRAM and becomes
effective when the switch reloads. Unlike the system MTU routing configuration, the MTU settings
you enter with the system mtu and system mtu jumbo commands are not saved in the switch Cisco
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.
In a switch stack, the MTU values applied to the members depend on the stack configuration:
• A stack consisting of only Catalyst 3750-X, Catalyst 3750-E, or Catalyst 3750 switches, also
referred to as a Catalyst 3750-X-only, Catalyst 3750-X-only, or Catalyst 3750-only stack
• A stack consisting of Catalyst 3750-X and Catalyst 3750-E switches or either of these and
Catalyst 3750 switches, also referred to as a mixed hardware stack
Table 13-5 shows how the MTU values are applied depending on the configuration.
Tab le 13-5 System MTU Values
Configuration system mtu command system jumbo mtu command system routing mtu command
Standalone Catalyst
3750-X, 3750-E, 3560-X
or 3560-E switch or
Catalyst 3750-X-only or
Catalyst 3750-E-only
stack
You can enter the command on
on a Catalyst 3750-X,
Catalyst 3750-E, Catalyst
3560-X, or Catalyst 3560-E
switch, but system MTU value
does not take effect. 1
Use the system mtu jumbo
bytes command.
The range is from 1500 to 9198
bytes.
Use the system mtu routing
bytes command.
The range is from 1500 to the
system jumbo MTU value (in
bytes).2
Mixed hardware stack Use the system mtu bytes
command, which takes effect
only on Catalyst 3750
members.1
The range is from 1500 to 1998
bytes.
Use the system mtu jumbo
bytes command.
The range is from 1500 to 9000
bytes.
Use the system mtu routing
bytes command.
The range is from 1500 to the
system MTU value (in bytes).2