Nexus 7k - 3750G VPC - High input discards RX side

[molinek]

Greetings, we have high input discards daily

on our VPC's that go to 3750G access stacks. One 3750G is running

src-dst-ip and the other stack is src-mac, both are increasing the input discard counter on the Nexus side, but not on the 3750 side. I have 4948-10G and UCS VPC's that are totally clean on both sides, just these 3750G's reporting issues.

The duplex settings are auto neg at 1GB. What does it mean when one side gets RX input discards and the other side is clean?

Thanks!

Kevin Moline

Nexus7K-A# sh vpc statistics vpc 21

port-channel21 is up

vPC Status: vPC number: 21

  Hardware: Port-Channel, address: 0024.f71d.3914 (bia 0024.f71d.3914)

  Description: *** port channel to CISCOL2-02 stack ***

  MTU 1500 bytes, BW 2000000 Kbit, DLY 10 usec,

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

  Encapsulation ARPA

  Port mode is trunk

  full-duplex, 1000 Mb/s

  Input flow-control is off, output flow-control is off

  Switchport monitor is off

  Members in this channel: Eth10/5, Eth10/6

  Last clearing of "show interface" counters never

  30 seconds input rate 903672 bits/sec, 396 packets/sec

  30 seconds output rate 3085632 bits/sec, 792 packets/sec

  Load-Interval #2: 5 minute (300 seconds)

    input rate 967.82 Kbps, 198 pps; output rate 3.00 Mbps, 693 pps

  RX

    2499364493 unicast packets  22547072 multicast packets  42035785 broadcast packets

    2563947350 input packets  807335713881 bytes

    0 jumbo packets  0 storm suppression packets

    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  20163146 input discard

    0 Rx pause

  TX

    3379827328 unicast packets  579669388 multicast packets  819525878 broadcast packets

    4779022594 output packets  1823328519547 bytes

    0 jumbo packets

    0 output error  0 collision  0 deferred  0 late collision

    0 lost carrier  0 no carrier  0 babble

    0 Tx pause

  1 interface resets

Nexus7K-A# sh vpc statistics vpc 22

port-channel22 is up

vPC Status: vPC number: 22

  Hardware: Port-Channel, address: 0024.f71d.3910 (bia 0024.f71d.3910)

  Description: *** port channel to L2 9-stack ***

  MTU 1500 bytes, BW 4000000 Kbit, DLY 10 usec,

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

  Encapsulation ARPA

  Port mode is trunk

  full-duplex, 1000 Mb/s

  Input flow-control is off, output flow-control is off

  Switchport monitor is off

  Members in this channel: Eth10/1, Eth10/2, Eth10/3, Eth10/4

  Last clearing of "show interface" counters never

  30 seconds input rate 18598536 bits/sec, 8613 packets/sec

  30 seconds output rate 43301808 bits/sec, 15642 packets/sec

  Load-Interval #2: 5 minute (300 seconds)

    input rate 21.55 Mbps, 8.91 Kpps; output rate 54.20 Mbps, 16.53 Kpps

  RX

    127720532005 unicast packets  32962230 multicast packets  111702675 broadcast packets

    127865196904 input packets  88136394079630 bytes

    0 jumbo packets  0 storm suppression packets

    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  13442373 input discard

    0 Rx pause

  TX

    312987953559 unicast packets  568610668 multicast packets  749863821 broadcast packets

    314306428048 output packets  239233492006027 bytes

    0 jumbo packets

    0 output error  0 collision  0 deferred  0 late collision

    0 lost carrier  0 no carrier  0 babble

    0 Tx pause

  1 interface resets

[kitanaka · Accepted solution]

Hello Kevin Moline,

Allowed vlans at the nexus side and the catalyst side are identical ?

There is a known issue that allowed vlan miss match causes "input discards" on nexus side.

Incoming traffic that has dot1q tag which is not allowed at nexus side is accounted in "input discard".

Regards,

Kimihito.

[molinek]

Hello, thanks for the quick reply. Both ends are full trunk.

(2) member stack  3750G Po21 -> Nexus7ks po21 (VPC21) full trunk

(9) member stack 3750G Po22 -> Nexus7ks Po22 (VPC22 full trunk

[kitanaka · Accepted solution]

Hello Kevin Moline,

Are those "input discard" counters incrementing at a fixed rate, or you see bursty increments ?

From when it started incrementing ? Was there any change at that time ?

Also are you able to grab following outputs ?

# Nexus

- Multiple shots of commands below during the increments.

show interface ethernet
show interface ethernet counters detailed all
show hardware internal errors module
show hardware internal statistics pktflow dropped
show interface ethernet counters errors
show hardware internal statistics module device mac all

- Single shot of commands below.
show interface ethernet capabilities
show interface ethernet switchport
show system internal ethpm info interface ethernet
show version
show port-channel summary
show interface trunk
show interface brief
show vpc consistency-parameters vpc 21
show vpc consistency-parameters vpc 22

# Catalyst

- Multiple shots of commands below during the increments.
show interfaces gigabitEthernet counters
show interfaces gigabitEthernet counters errors
show interfaces gigabitEthernet controller

- Single shot of commands below.
show interfaces gigabitEthernet switchport
show interfaces gigabitEthernet capabilities
show version
show interfaces trunk

Thanks and regards,

Kimihito.

[molinek]

Hello, thanks for the response. I will be posting this information today.

Kevin

[molinek]

I have the files that you requested, how do you want me to get them to you? There are several files...

[kitanaka]

Hello Kevin Moline,

I just sent a reply for the unicast message from you. Could you pls check your mail box ?

Regards,

Kimihito.

[Jlwireman_2]

I'm havine the same issue on a Pair of Nexus, no VPC just a trunk link. My input discards are 100-200k per hour.

TAC had me make sure my vlan allow lists match but still having the same issue.

I'm using this card

sh module 10
Mod  Ports  Module-Type                      Model              Status
---  -----  -------------------------------- ------------------ ------------
10   48     10/100/1000 Mbps Ethernet Module N7K-M148GT-11      ok

Mod  Sw              Hw
---  --------------  ------
10   4.2(3)          1.3    

And running System version: 4.2(3)

Just curious what version of code are you running?

[kitanaka · Accepted solution]

Hello Kevin Moline,

Could you have a chance to check the private message that I sent a couple of days ago ?

Regards,

Kimihito.

[melchib]

I have seen this issue before as well - even with vlan's matching up on both sides of the link.  (3750G to Nexus 7k - vPC).

Was there ever a resolution or explanation?

Brad

[darrenriley5]

Very interesting, I'm seeing the same problem myself. I have an etherchannel between two Nexus 7K's (not vpc). On one switch its reporting high input discards on the RX side. I've checked the etherchannel which is configured with the same allowed vlans.

Each N7K then connects to a 3750 stack. The 3750 terminates our dfark fibre for inter site communication.