SMC Networks 7824M/FSW - annexe 1, Management Manual

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C
ONFIGURING THE
M
AXIMUM
F
RAME
S
IZE
4-5
CLI – This example sets the switch to operate in QinQ mode.
Configuring the Maximum Frame Size
The maximum transfer unit (or frame size) for traffic crossing the switch
should be set to minimize unnecessary fragmentation and maximize the
transfer of large sequential data streams.
Command Usage
• Fast Ethernet ports are only affected by the System MTU setting.
• Gigabit Ethernet ports are only affected by the Jumbo frame size setting.
• The switch provides more efficient throughput for large sequential data
transfers by supporting jumbo frames on Gigabit Ethernet ports of up
to 9216 bytes. Compared to standard Ethernet frames that run only up
to 1.5 KB, using jumbo frames for Gigabit Ethernet significantly reduces
the per-packet overhead required to process protocol encapsulation
fields.
• Frame sizes for Fast Ethernet ports can be extended up to 1546 bytes,
and are used primarily to allow for additional header fields – not to
significantly increase the per-packet data size. These Fast Ethernet
extended fames and are more often called “baby jumbo frames.”
• To use jumbo frames, both the source and destination end nodes (such
as a computer or server) must support this feature. Also, when the
connection is operating at full duplex, all switches in the network
between the two end nodes must be able to accept the extended frame
size. And for half-duplex connections, all devices in the collision domain
would need to support jumbo frames.
• After setting the jumbo frame size, remember to implement the new
setting by enabling jumbo frames as described in the next section.
Console(config)#system mode qinq
19-10
Console(config)#exit
Console#show system mode
19-11
System mode is QinQ mode
Console#