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New Member

Nexus 5596UP - Jumbo frames TX even though jumbo frames not enabled?

Could someone tell me why this port is sending Jumbo Packets even though jumbo frames are not enabled on the switch?  I'm trying to trouble shoot an issue with a server not being able to transfer at wire speed.


Ethernet1/35 is up
 Dedicated Interface
  Belongs to Po751
  Hardware: 1000/10000 Ethernet, address: 547f.eeb0.1baa (bia 547f.eeb0.1baa)
  Description: x
  MTU 1500 bytes, BW 10000000 Kbit, DLY 10 usec
  reliability 255/255, txload 1/255, rxload 1/255
  Encapsulation ARPA
  Port mode is trunk
  full-duplex, 10 Gb/s, media type is 10G
  Beacon is turned off
  Input flow-control is off, output flow-control is off
  Rate mode is dedicated
  Switchport monitor is off
  EtherType is 0x8100
  Last link flapped 33week(s) 2day(s)
  Last clearing of "show interface" counters never
  1 interface resets
  30 seconds input rate 221920 bits/sec, 71 packets/sec
  30 seconds output rate 216968 bits/sec, 177 packets/sec
  Load-Interval #2: 5 minute (300 seconds)
    input rate 419.02 Kbps, 57 pps; output rate 570.33 Kbps, 192 pps
    19339643291 unicast packets  22999366 multicast packets  2241049 broadcast packets
    19364883706 input packets  8219619292920 bytes
    1440124319 jumbo packets  0 storm suppression bytes
    0 runts  0 giants  0 CRC  0 no buffer
    0 input error  0 short frame  0 overrun   0 underrun  0 ignored
    0 watchdog  0 bad etype drop  0 bad proto drop  0 if down drop
    0 input with dribble  0 input discard
    0 Rx pause
    19419081143 unicast packets  632675822 multicast packets  553773489 broadcast packets
    20605530454 output packets  9077525431634 bytes
    2145386732 jumbo packets
    0 output errors  0 collision  0 deferred  0 late collision
    0 lost carrier  0 no carrier  0 babble 0 output discard
    0 Tx pause



New Member

Opened a ticket with Cisco

Opened a ticket with Cisco and this is what they pointed me to.  I just wanted to update this post with the solution.


New Member

Note that the commandsh

Note that the command

sh hardware internal carmel port ethernet 1/1 counters rx
breaks down counters for a port by many different frame sizes.
At one point TAC mentioned to me that a frame could be 1518 bytes when it leaves a host, but when a dot1q tag is inserted, that can push the total frame size just over 1518.  The switch could then count it as a jumbo even if it truly isn't jumbo.
If anyone has more info on this notion, I would be very interested in hearing it.