Cisco Catalyst Blade Switch 3020 for HP Software Configuration Guide, Rel. 12.2(25)SEF1

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Cisco Catalyst Blade Switch 3020 for HP Software Configuration Guide
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Chapter 8 Configuring Interface Characteristics
Configuring the System MTU
Configuring the System MTU
The default maximum transmission unit (MTU) size for frames received and transmitted 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.
Gigabit Ethernet ports are not affected by the system mtu command; 10/100 ports are not affected by
the system jumbo mtu command. 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 or jumbo MTU size, you must reset the switch
before the new configuration takes effect.
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, 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 jumbo mtu 1800
Switch(config)# exit
Switch# reload
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 Mbps. 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.