Specifications

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Catalyst 2970 Switch Software Configuration Guide
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Chapter 9 Configuring Interface Characteristics
Configuring the System MTU
Adding a Description for an Interface
You can add a description about an interface to help you remember its function. The description appears
in the output of these privileged EXEC commands: show configuration
, show running-config, and
show interfaces.
Beginning in privileged EXEC mode, follow these steps to add a description for an interface:
Use the no description interface configuration command to delete the description.
This example shows how to add a description on Gigabit Ethernet interface 0/3 and to verify the
description:
Switch# config terminal
Enter configuration commands, one per line. End with CNTL/Z.
Switch(config)# interface GigabitEthernet0/3
Switch(config-if)# description Connects to Marketing
Switch(config-if)# end
Switch# show interfaces GigabitEthernet0/3 description
Interface Status Protocol Description
Gi0/3 admin down down Connects to Marketing
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.
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 MTU size, you must reset the switch before the new
configuration takes effect.
The size of frames that can be received by the switch CPU is limited to 1500 bytes, no matter what value
was entered with the system mtu or system mtu jumbo commands. Although frames that are forwarded
typically are not received by the CPU, in some cases packets are sent to the CPU, such as traffic sent to
control traffic, SNMP, or Telnet.
Command Purpose
Step 1
configure terminal Enter global configuration mode.
Step 2
interface interface-id Enter interface configuration mode, and enter the interface for which
you are adding a description.
Step 3
description string Add a description (up to 240 characters) for an interface.
Step 4
end Return to privileged EXEC mode.
Step 5
show interfaces interface-id description
or
show running-config
Verify your entry.
Step 6
copy running-config startup-config (Optional) Save your entries in the configuration file.