12-03-2011 08:05 PM - edited 03-07-2019 03:43 AM
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
12-04-2011 02:42 AM
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:
Please note the problem is probably on the device receiving the potentially oversized frames.
regards,
Leo
12-06-2011 11:01 AM
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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