One side has only input errors, the other side only output errors. Why?

[Blackschwanzer]

Hello.

We have 2 Cisco multi-layer switches SW1 and SW2 connected via trunk link.

On the SW1 there are 9905 input errors (and the count is increasing) and 0 output errors, on the SW2 there are 13511 output errors (and the count is increasing) and 0 input errors.

The cabling and transceivers were checked on both sides and no issues found.

Question - which switch could be causing problems? The one with increasing INPUT errors or the one with OUTPUT errors? Or is it not possible?

I am interested why on the one side there are only input errors and on the other side there are only output errors?

Thank you.

[Leo Laohoo]

---

@Blackschwanzer wrote:

Question - which switch could be causing problems? The one with increasing INPUT errors or the one with OUTPUT errors? Or is it not possible?

---

Is it possible?  Yes. 

What's causing it?  Most likely duplex mismatch. 

Post the complete output to the command "sh interface <BLAH> controll" from both interfaces.

[Blackschwanzer]

I only have these choices:

SW1# sh int Ethernet2/1 ?
<CR>
, Multi range separator
- Range separator
. Sub interface separator
> Redirect it to a file
>> Redirect it to a file in append mode
brief Show brief info of interface
cable-diagnostics-tdr Show interface tdr test information
capabilities Show interface capabilities information
counters Show interface counters
debounce Show interface debounce time information
description Show interface description
fcoe (no abbrev) Show FCoE info for interface
fex-intf Show FEX ports pinned to fabric port
flowcontrol Show interface flowcontrol information
mac-address Show interface MAC address
priority-flow-control Show interface PFC information
status Show interface line status
switchport Show interface switchport information
transceiver Show interface transceiver information
trunk Show interface trunk information
| Pipe command output to filter

Cisco Nexus Operating System (NX-OS) Software

SW1# sh int Ethernet2/1
Ethernet2/1 is up
Hardware: 1000/10000 Ethernet, address: aaaa.bbbb.cccc(aaaa.bbbb.cccc)
Description: link to SW2
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 6d05h
Last clearing of "show interface" counters 6d04h
30 seconds input rate 8504 bits/sec, 1063 bytes/sec, 4 packets/sec
30 seconds output rate 3352 bits/sec, 419 bytes/sec, 3 packets/sec
Load-Interval #2: 1 minute (60 seconds)
input rate 9.76 Kbps, 4 pps; output rate 3.38 Kbps, 3 pps
RX
899853 unicast packets 2344756 multicast packets 552386 broadcast packets
3796995 input packets 1451895260 bytes
386344 jumbo packets 0 storm suppression bytes
0 runts 0 giants 10590 CRC 0 no buffer
10590 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
TX
195959 unicast packets 2078719 multicast packets 174085 broadcast packets
2448763 output packets 278494074 bytes
3317 jumbo packets
0 output errors 0 collision 0 deferred 0 late collision
0 lost carrier 0 no carrier 0 babble
0 Tx pause
0 interface resets

SW2:

SW2# sh int Ethernet2/1
Ethernet2/1 is up
Hardware: 1000/10000 Ethernet, address: cccc.bbbb.aaaa
Description: link to SW1
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 6d05h
Last clearing of "show interface" counters never
30 seconds input rate 3784 bits/sec, 473 bytes/sec, 3 packets/sec
30 seconds output rate 8104 bits/sec, 1013 bytes/sec, 4 packets/sec
Load-Interval #2: 1 minute (60 seconds)
input rate 3.61 Kbps, 3 pps; output rate 6.65 Kbps, 3 pps
RX
43345641 unicast packets 678101970 multicast packets 87216621 broadcast packets
808664232 input packets 99408129663 bytes
3459513 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
TX
49337558 unicast packets 1811296371 multicast packets 614367171 broadcast packets
2475001100 output packets 363344229566 bytes
11372626 jumbo packets
14195 output errors 0 collision 0 deferred 0 late collision
0 lost carrier 0 no carrier 0 babble
0 Tx pause
2 interface resets

[Leo Laohoo]

Hmmmm ... 10 Gbps SFP module.
Check (and replace) the SFP+ at SW2.

[mlund]

Hi

I'm just thinking loud now. If this is a nexus switch, the switching mode is cut-through, so if there are traffic with errors on an incoming interface ( another interface) that traffic will be cut-through switched to this interface before the incoming interface have done the CRC check. So when the hole frame have been delivered the switch will then see that the frame has an invalid CRC, and so increase the output error counter.

Maybe the switch also count that error on the incoming interface.

Can you look at the other interfaces to see if there are errors.

/Mikael