User guide

E
XTREME
W
ARE
S
OFTWARE
U
SER
G
UIDE
4-7
J
UMBO
F
RAMES
J
UMBO
F
RAMES
Jumbo frames are Ethernet frames that are larger than 1523 bytes, including four bytes
used for the cyclic redundancy check (CRC). Extreme products that use the “i” chipset
support switching and routing of jumbo frames at wire-speed on all ports.
Jumbo frames are used between endstations that support larger frame sizes for more
efficient transfers of bulk data. Both endstations involved in the transfer must be
capable of supporting jumbo frames. The switch does not perform IP fragmentation, or
participate in MTU negotiation on behalf of devices that do not support jumbo frames.
E
NABLING
J
UMBO
F
RAMES
To enable jumbo frame support, you must configure the maximum MTU size of a jumbo
frame that will be allowed by the switch. To set the maximum MTU size, use the
following command
config jumbo-frame size <jumbo_frame_mtu>
The jumbo_frame_mtu range is 1523 to 9216. The value describes the maximum size
“on the wire,” and includes 4 bytes of CRC plus another 4 bytes if 802.1Q tagging is
being used.
Next, enable support on the physical ports that will carry jumbo frames, using the
following command:
enable jumbo-frame ports [<portlist | all]
Some network interface cards (NICs) have a configured maximum MTU size that
does not include the additional 4 bytes of CRC. Ensure that the NIC maximum
MTU size is at or below the maximum MTU size configured on the switch.
Frames that are larger than the MTU size configured on the switch are dropped
at the ingress port.
L
OAD
S
HARING ON THE
B
LACK
D
IAMOND AND
A
LPINE
S
WITCH
Load sharing with BlackDiamond or Alpine switches allows you to increase bandwidth
and resiliency by using a group of ports to carry traffic in parallel between switches.
The sharing algorithm allows the switch to use multiple ports as a single logical port.