Cisco Gigabit Ethernet Switch Module for HP BladeSystem p-Class Command Reference Guide

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Cisco Gigabit Ethernet Switch Module for the HP p-Class Blade System Command Reference Guide

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Chapter 2 CGESM Switch Cisco IOS Commands

system mtu

Use the system mtu global configuration command to set the maximum packet size or maximum

transmission unit (MTU) size for Gigabit Ethernet ports or for 10/100 ports. Use the no form of this

command to restore the global MTU value to its default value.

system mtu {bytes | jumbo bytes}

no system mtu

Syntax Description

Defaults The default MTU size for all ports is 1500 bytes.

Command Modes Global configuration

Command History

Usage Guidelines When you use this command to change the system MTU or jumbo MTU size, you must reset the switch

before the new configuration takes effect.

Gigabit Ethernet ports are not affected by the system mtu command, and 10/100-Mb/s ports are not

affected by the system mtu jumbo command.

If you enter a value that is outside the range for the specific type of switch, the value is not accepted.

Note The switch does not support setting the MTU on a per-interface basis.

The size of frames that can be received by the switch CPU is limited to 1998 bytes, regardless of the

value entered with the system mtu command. Although forwarded or routed frames are usually not

received by the CPU, some packets (for example, control traffic, SNMP, Telnet, and routing protocols)

are sent to the CPU.

Because the switch does not fragment packets, it drops switched packets larger than the packet size

supported on the egress interface.

For example, if the system mtu value is 1998 bytes and the system mtu jumbo value is 5000 bytes,

packets up to 5000 bytes can be received on interfaces operating at 1000 Mb/s. However, although a

packet larger than 1998 bytes can be received on an interface operating at 1000 Mb/s, if its destination

interface is operating at 10 or 100 Mb/s, the packet is dropped.

bytes The range is 1500 to 1998 bytes. This is the maximum MTU received at

10/100-Mb/s Ethernet switch ports.

jumbo bytes The range is 1500 to 9000 bytes. This is the maximum MTU received at the

physical port for Gigabit Ethernet ports.

Release Modification

12.2(25)SE1 This command was introduced.