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Catalyst 2960 and 2960-S Switch Software Configuration Guide
OL-8603-09
Chapter 12 Configuring Interface Characteristics
Configuring the System MTU
Beginning in privileged EXEC mode, follow these steps to configure a Layer 3 SVI:
To remove an IP address from an SVI, use the no ip address interface configuration command.
This example shows how to configure a Layer 3 SVI and to assign it an IP address:
Switch# configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Switch(config)# interface vlan 33
Switch(config-if)# ip address 192.20.135.21 255.255.255.0
Configuring the System MTU
The default maximum transmission unit (MTU) size for frames received and transmitted on all interfaces
is 1500 bytes. You can increase the MTU size for all interfaces operating at 10 or 100 Mb/s 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 mtu jumbo 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 E thernet
interfaces. 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, or Telnet.
Note If Layer 2 Gigabit Ethernet interfaces are configured to accept frames greater than the 10/100 interfaces,
jumbo frames received on a Layer 2 Gigabit Ethernet interface and sent on a Layer 2 10/100 interface
are dropped.
Command Purpose
Step 1 configure terminal Enter global configuration mode.
Step 2 interface vlan vlan-id Specify the VLAN to be configured as a Layer 3 SVI,
and enter interface configuration mode.
Step 3 ip address ip_address subnet_mask Configure the IP address and IP subnet.
Step 4 end Return to privileged EXEC mode.
Step 5 show interfaces [interface-id]
show ip interface [interface-id]
show running-config interface [interface-id]
Verify the configuration.
Step 6 copy running-config startup-config (Optional) Save your entries in the configuration file.