6-13
Cisco 7600 Series Router Cisco IOS Software Configuration Guide—12.1E
78-14064-04
Chapter 6 Configuring Interfaces
Configuring Optional Interface Features
Release 12.1(13)E and later releases support nondefault MTU sizes between 1,500 and 9,216 bytes for
Layer 2 Ethernet ports, configured per-port with the mtu command and globally with the
system jumbomtu command.
With earlier releases, 9216 bytes is the only supported nondefault MTU size for Layer 2 Ethernet ports,
configured per-port with the mtu command.
VLAN Interfaces
You can configure a different MTU size on each Layer 3 VLAN interface. Configuring a nondefault
MTU size on a VLAN interface limits traffic to the nondefault MTU size.
You can configure the MTU size on VLAN interfaces to support jumbo frames with the following
hardware and software:
• Supervisor Engine 1 and Release 12.1(7)E or later
• Supervisor Engine 2 and Release 12.1(8a)E or later
Configuring MTU Sizes
These sections describe how to configure MTU sizes:
• Configuring MTU Sizes, page 6-13
• Configuring the Global LAN Port MTU Size, page 6-14
Configuring the MTU Size
To configure the MTU size, perform this task:
When configuring the MTU size, note the following syntax information:
• For VLAN interfaces and Layer 3 Ethernet ports, supported MTU values are from 64 to 9216 bytes.
• For Layer 2 Ethernet ports with Release 12.1(13)E and later releases, you can configure only the
global egress LAN port MTU size (see the “Configuring the Global LAN Port MTU Size” section
on page 6-14).
• For Layer 2 Ethernet ports with earlier releases, the only supported MTU size is 9216 bytes.
Command Purpose
Step 1
Router(config)# interface {{vlan vlan_ID} |
{{type
1
slot/port} | {port-channel
port_channel_number} slot/port}}
1. type = ethernet, fastethernet, gigabitethernet, tengigabitethernet, or ge-wan
Selects the interface to configure.
Step 2
Router(config-if)# mtu mtu_size
Configures the MTU size.
Router(config-if)# no mtu
Reverts to the default MTU size (1500 bytes).
Step 3
Router(config-if)# end
Exits configuration mode.
Step 4
Router# show running-config interface
[{gigabitethernet | tengigabitethernet}
slot/port]
Displays the running configuration.
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