The Nexus 5000 is a cut-through switch at 10 Gb/s. This means that an MTU can be checked, but the frame will already be transmitting before the length is known. Therefore, the frame cannot be dropped. The frame is truncated after the MTU is reached and the CRC value is stomped. The ingress interface increments an Rx Jumbo and the egress interface will increment a Tx CRC and a Tx Jumbo.
•If jumbo frames are seen with the show interface or the show hardware internal gatos port ethernet 1/1 counters rx commands, this is not an indication that the frames are being dropped. A jumbo frame is just an Ethernet frame, greater than 1500 bytes, that was received or transmitted.
•The <b>show queuing interface <i>ex/y</i></b> command shows the current configured MTU (per class).
•A drop due to an MTU violation can be seen with the show hardware internal gatos counters interrupt match mtu* command.
•A counter that matches the Gatos number and fw_instance from the show hardware internal gatos port ethernet 1/1 | include instance|mac command is the indicator that an MTU violation has taken place and that the frame has been stomped.
•If jumbo frames are seen with the show interface or the show hardware internal gatos port ethernet 1/1 counters rx commands, this is not an indication that the frames are being dropped. A jumbo frame is just an Ethernet frame, greater than 1500 bytes, that was received or transmitted.
•The <b>show queuing interface <i>ex/y</i></b> command shows the current configured MTU (per class).
•A drop due to an MTU violation can be seen with the show hardware internal gatos counters interrupt match mtu* command.
•A counter that matches the Gatos number and fw_instance from the show hardware internal gatos port ethernet 1/1 | include instance|mac command is the indicator that an MTU violation has taken place and that the frame has been stomped.
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