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Cisco Catalyst Blade Switch 3030 Command Reference
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Chapter 2 Cisco
Catalyst
Blade Switch 3030 Cisco IOS Commands
system mtu
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. 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 operating at 1000 Mbps are not affected by the
system mtu
command, and
10/100-Mbps 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 Mbps. However, although a
packet larger than 1998 bytes can be received on an interface operating at 1000 Mbps, if its destination
interface is operating at 10 or 100 Mbps, the packet is dropped.
bytes
The range is 1500 to 1998 bytes. This is the maximum MTU received at
10/100-Mbps Ethernet switch ports.
jumbo
bytes
Set the system jumbo MTU for Gigabit Ethernet ports operating at 1000
Mbps or greater. 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)SEE
This command was introduced.