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3750-X + C3KX-NM-10G = oddness

darenv
Level 1
Level 1

Folks

We have a brand new 2 x 3750-X stack running 15.0(1)SE3 with C3KX-NM-10Gs installed in each switch.  An HP C-Class server enclosure with Virtual Connect Flex-10 modules is connected to each of the 10G ports using twinax cables and they seem to behave OK apart from some random packet drop which appears to be within the enclosure and not without.  However, when we were investigating this, we found a little oddity ... even though we have jumbo frame support enabled on the 3750-Xs, we are getting a significant "Valid frames, too large" recieved count on the interface, and a "Too large" transmitted count.  I've looked around and can't find a definitive reason for this count to go up - it doesn't seem to be a jumbo frames thing, more an unexpected-additional-field-in-a-header type thing, like when you have a VLAN tag in a DTP frame.  Any thoughts as to why I might be getting these from a new server enclosure?

SW-STACK-CORE-3750X#sho int t2/1/1 controller              

TenGigabitEthernet2/1/1 is up, line protocol is up (connected)

  Hardware is Ten Gigabit Ethernet, address is a44c.116e.55b5 (bia a44c.116e.55b5)

  Description: *** Server Enclosure B2P3 ***

  MTU 9000 bytes, BW 10000000 Kbit/sec, DLY 10 usec,

     reliability 255/255, txload 1/255, rxload 1/255

  Encapsulation ARPA, loopback not set

  Keepalive not set

  Full-duplex, 10Gb/s, link type is auto, media type is SFP-10GBase-CX1

  input flow-control is off, output flow-control is unsupported

  ARP type: ARPA, ARP Timeout 04:00:00

  Last input 00:00:05, output 00:00:00, output hang never

  Last clearing of "show interface" counters 2d15h

  Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0

  Queueing strategy: fifo

  Output queue: 0/40 (size/max)

  5 minute input rate 3453000 bits/sec, 1142 packets/sec

  5 minute output rate 6076000 bits/sec, 1064 packets/sec

     52092348 packets input, 20546616470 bytes, 0 no buffer

     Received 15193 broadcasts (15193 multicasts)

     0 runts, 0 giants, 0 throttles

     0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored

     0 watchdog, 15193 multicast, 0 pause input

     0 input packets with dribble condition detected

     45009519 packets output, 23719388911 bytes, 0 underruns

     0 output errors, 0 collisions, 0 interface resets

     7596 unknown protocol drops

     0 babbles, 0 late collision, 0 deferred

     0 lost carrier, 0 no carrier, 0 pause output

     0 output buffer failures, 0 output buffers swapped out

     Transmit TenGigabitEthernet2/1/1         Receive

  23722640051 Bytes                      20546716139 Bytes                   

     43629235 Unicast frames                52077194 Unicast frames          

       393269 Multicast frames                 15935 Multicast frames  &nbs