KB.15.15

Troubleshooting

A VLAN is configured to allow jumbo frames, but one or more ports drops all inbound jumbo frames

The port may not be operating at a minimum of 10 Mbps on the HP 3500 switches or 1 Gbps on

the other switches covered in this guide. Regardless of a port's configuration, if it is actually

operating at a speed lower than 10 Mbps for HP 3500 switches or 1 Gbps for the other switches,

it drops inbound jumbo frames. For example, if a port is configured for Auto mode (speed-duplex

auto), but has negotiated a 7 Mbps speed with the device at the other end of the link, the port

cannot receive inbound jumbo frames. 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 frames" messages in the Event Log

The switches can transmit outbound jumbo traffic 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 forwarding

jumbo frames received on the jumbo VLAN to non-jumbo ports.

Jumbo frames 195