HP Cisco Catalyst Blade Switch 3020 Cisco Catalyst Blade Switch 3020 for HP So - Page 228

Configuring the System MTU

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Configuring the System MTU Chapter 8 Configuring Interface Characteristics 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: Step 1 Step 2 Command configure terminal system mtu bytes Step 3 system mtu jumbo bytes Step 4 Step 5 Step 6 end copy running-config startup-config reload Purpose Enter global configuration mode. (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. (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. Return to privileged EXEC mode. Save your entries in the configuration file. Reload the operating system. 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 8-18 Cisco Catalyst Blade Switch 3020 for HP Software Configuration Guide OL-8915-01

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8-18
Cisco Catalyst Blade Switch 3020 for HP Software Configuration Guide
OL-8915-01
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.