13-18
Cisco IE 3000 Switch Software Configuration Guide
OL-13018-03
Chapter 13 Configuring Interface Characteristics
Monitoring and Maintaining the Interfaces
Frames sizes that can be received by the switch CPU are limited to 1998 bytes, no matter what value was
entered with the
system mtu
or
system mtu jumbo
commands. Although frames that are forwarded are
typically not received by the CPU, in some cases packets are sent to the CPU, such as traffic sent to
control traffic, SNMP, or Telnet.
Note
If Gigabit Ethernet interfaces are configured to accept frames greater than the 10/100 interfaces, jumbo
frames received on a Gigabit Ethernet interface and sent on a 10/100 interface are dropped.
Beginning in privileged EXEC mode, follow these steps to change MTU size for all 10/100 or Gigabit
Ethernet interfaces:
If you enter a value that is outside the allowed range for the specific type of interface, the value is not
accepted.
Once the switch reloads, you can verify your settings by entering the
show system mtu
privileged EXEC
command.
This example shows how to set the maximum packet size for a Gigabit Ethernet port to 1800 bytes:
Switch(config)#
system mtu jumbo 1800
Switch(config)#
exit
Switch#
reload
This example shows the response when you try to set Gigabit Ethernet interfaces to an out-of-range
number:
Switch(config)#
system mtu jumbo 25000
^
% Invalid input detected at '^' marker.
Monitoring and Maintaining the Interfaces
These sections contain interface monitoring and maintenance information:
•
Monitoring Interface Status, page 13-19
•
Clearing and Resetting Interfaces and Counters, page 13-19
•
Shutting Down and Restarting the Interface, page 13-20
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
system mtu
bytes
(Optional) Change the MTU size for all interfaces on
the switch that are operating at 10 or 100 Mb/s. The
range is 1500 to 1998 bytes; the default is 1500 bytes.
Step 3
system mtu
jumbo
bytes
(Optional) Change the MTU size for all Gigabit
Ethernet interfaces on the switch. The range is 1500 to
9000 bytes; the default is 1500 bytes.
Step 4
end
Return to privileged EXEC mode.
Step 5
copy running-config startup-config
Save your entries in the configuration file.
Step 6
reload
Reload the operating system.
