12-35
Catalyst 3750-E and 3560-E Switch Software Configuration Guide
OL-9775-08
Chapter 12 Configuring Interface Characteristics
Configuring the System MTU
–
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
• 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
e
ffective 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 12-5 sh
ows how the MTU values are applied depending on the configuration.
Ta b l e 12-5 System MTU Values
Configuration system mtu command system jumbo mtu command system routing mtu command
Standalone Catalyst
3
750-X, 3750-E, 3560-X
or 3560-E switch or
Catalyst 3750-X-only or
Ca
talyst 3750-E-only
stack
You can enter the command on
o
n a Catalyst 3750-X,
Catalyst 3750-E, Catalyst
3
560-X, or Catalyst 3560-E
switch, but system MTU value
does not take effect.
1
1. If you use the system mtu bytes command on a Catalyst 3750-X or 3750-E member in a mixed hardware stack, the setting takes effect on the Fast Ethernet
ports of Catalyst
3750 members.
Use the system mtu jumbo
bytes command.
The range is from 1500 to 9198
by
tes.
Use the syste
m mtu routing
bytes command.
The range is from 1500 to the
sy
stem jumbo MTU value (in
bytes).
2
2. The system routing MTU value is the applied value, not the configured value.
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 syste
m mtu jumbo
bytes command.
The range is from 1500 to 9000
by
tes.
Use the syste
m mtu routing
bytes command.
The range is from 1500 to the
sy
stem MTU value (in bytes).
2
Catalyst 3750-only stack
Catalyst 3750 switch
Catalyst 3560 switch
Use the system mtu bytes
command.
The range is from 1500 to 1998
by
tes.
Use the syste
m mtu jumbo
bytes command.
The range is from 1500 to 9000
by
tes.
Use the syste
m mtu routing
bytes command.
The range is from 1500 to the
sy
stem MTU value (in bytes).
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