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outDiscard errors on vmware and iscsi ports

I have been battling high amounts of outDiscards on ports connected to vmware and iscsi hosts. I have verified there is no speed/duplex mismatch. I am not seeing any interface errors on on the vmware or iscsi host.

We have brand new Cisco 2960-s switches. Before we migrated to the Ciscos we were using 3com switches without error.

The only thing that has changed is on the vmware hosts trunking iSCSI traffic on the same physical port as the rest of the traffic. Could this cause this problem or am I missing something else?

I just cleared the counter errors a few minutes before:

Gi0/15              0           0           0           0          0          144   <------ iscsi host interface

sw1.e1#sh int gi0/15

GigabitEthernet0/15 is up, line protocol is up (connected)

  Hardware is Gigabit Ethernet, address is 1caa.0728.210f (bia 1caa.0728.210f)

  MTU 1500 bytes, BW 1000000 Kbit, DLY 10 usec,

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

  Encapsulation ARPA, loopback not set

  Keepalive set (10 sec)

  Full-duplex, 1000Mb/s, media type is 10/100/1000BaseTX

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

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

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

  Last clearing of "show interface" counters 1d00h

  Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 144

  Queueing strategy: fifo

  Output queue: 0/40 (size/max)

  5 minute input rate 364000 bits/sec, 81 packets/sec

  5 minute output rate 1541000 bits/sec, 146 packets/sec

     11311108 packets input, 7656725682 bytes, 0 no buffer

     Received 5897 broadcasts (0 multicasts)

     0 runts, 0 giants, 0 throttles

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

     0 watchdog, 0 multicast, 0 pause input

     0 input packets with dribble condition detected

     13791953 packets output, 15801431213 bytes, 0 underruns

     0 output errors, 0 collisions, 0 interface resets

     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

sw1.e1#sh controllers ethernet-controller gigabitEthernet 0/15

     Transmit GigabitEthernet0/15             Receive

   1443968205 Bytes                        276299593 Bytes                   

   2982816424 Unicast frames              2241107073 Unicast frames          

     37403195 Multicast frames                     0 Multicast frames        

      1499185 Broadcast frames                776815 Broadcast frames        

            0 Too old frames              4148378589 Unicast bytes           

            0 Deferred frames                      0 Multicast bytes         

            0 MTU exceeded frames           49716160 Broadcast bytes         

            0 1 collision frames                   0 Alignment errors        

            0 2 collision frames                   0 FCS errors              

            0 3 collision frames                   0 Oversize frames         

            0 4 collision frames                   0 Undersize frames        

            0 5 collision frames                   0 Collision fragments     

            0 6 collision frames      

            0 7 collision frames             1107205 Minimum size frames     

            0 8 collision frames          1604512388 65 to 127 byte frames   

            0 9 collision frames             1852194 128 to 255 byte frames  

            0 10 collision frames            5249104 256 to 511 byte frames  

            0 11 collision frames            7484488 512 to 1023 byte frames 

            0 12 collision frames           14651009 1024 to 1518 byte frames

            0 13 collision frames                  0 Overrun frames          

            0 14 collision frames                  0 Pause frames            

            0 15 collision frames     

            0 Excessive collisions                 0 Symbol error frames     

            0 Late collisions                      0 Invalid frames, too large

            0 VLAN discard frames          607027500 Valid frames, too large 

            0 Excess defer frames                  0 Invalid frames, too small

      1524553 64 byte frames                       0 Valid frames, too small 

    445828376 127 byte frames         

     36575564 255 byte frames                      0 Too old frames          

     64523185 511 byte frames                      0 Valid oversize frames   

     94700936 1023 byte frames                     0 System FCS error frames 

    146150422 1518 byte frames                     0 RxPortFifoFull drop frame

   2232415768 Too large frames        

            0 Good (1 coll) frames    

            0 Good (>1 coll) frames   

  • LAN Switching and Routing
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2 REPLIES

outDiscard errors on vmware and iscsi ports

The output shows a lot of too large frames in both directions. This may be the cause of your problem.

Expl: Because you are now tagging the iSCSI frames, their size will grow with four bytes. Depending on the actual MTU sizes, this may be slightly too large. The following link contains some information on the subject:

http://www.cisco.com/en/US/products/hw/switches/ps700/products_configuration_example09186a008010edab.shtml

Please note the problem is probably on the device receiving the potentially oversized frames.

regards,

Leo

New Member

outDiscard errors on vmware and iscsi ports

Leo,

Thanks for the input. I disabled all trunking for the storage interfaces last night. I am still seeing high discards on one of our vmware servers today though. There are no discards on the other vmware server or the iscsi SAN.

I cleared the counters 6 hours ago:

Gi0/14              0           0           0           0          0       100394

Any other Ideas? I was looking to see if I could set the mtu to 1500 on the specific port on the switch but it doesnt look like Cisco has an option for that.

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