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10-24
Port Status and Basic Configuration
Jumbo Packets
Troubleshooting
A VLAN is configured to allow jumbo packets, but one or more ports
drops all inbound jumbo packets. The port may not be operating at 1
gigabit or higher. Regardless of a port’s configuration, if it is actually operating
at a speed lower than 1 gigabit, it drops inbound jumbo packets. For example,
if a port is configured for Auto mode (speed-duplex auto), but has negotiated a
100 Mbps speed with the device at the other end of the link, then the port
cannot receive inbound jumbo packets. To determine the actual operating
speed of one or more ports, view the Mode field in the output for the following
command:
show interfaces brief < port-list >
A non-jumbo port is generating “Excessive undersize/giant packets”
messages in the Event Log. The switch can transmit outbound jumbo traf-
fic on any port, regardless of whether the port belongs to a jumbo VLAN. In
this case, another port in the same VLAN on the switch may be jumbo-enabled
through membership in a different, jumbo-enabled VLAN, and may be forward-
ing jumbo packets received on the jumbo VLAN to non-jumbo ports. Refer to
“Outbound Jumbo Traffic” on page 10-23.