Junos
Junos

Tail-dropped packets EX4200

‎02-12-2019 06:35 AM

Hello, i have 10 switchs EX4200-48T, and i got tail-drops on ge-0/0/ interfaces:

 

> show interfaces statistics | match Error | except Link-level | except "Output errors: 0" 
  Input errors: 0, Output errors: 6997
  Input errors: 0, Output errors: 428
  Input errors: 0, Output errors: 8424
  Input errors: 0, Output errors: 7107
  Input errors: 0, Output errors: 8544
  Input errors: 0, Output errors: 8731
  Input errors: 0, Output errors: 8299
  Input errors: 0, Output errors: 8225
  Input errors: 0, Output errors: 8252
  Input errors: 0, Output errors: 8402
  Input errors: 0, Output errors: 8330
  Input errors: 0, Output errors: 6992
  Input errors: 0, Output errors: 6981
  Input errors: 0, Output errors: 8136
  Input errors: 0, Output errors: 8461
  Input errors: 0, Output errors: 8093
  Input errors: 0, Output errors: 8075
  Input errors: 0, Output errors: 8265
  Input errors: 0, Output errors: 8298
  Input errors: 0, Output errors: 8380
  Input errors: 0, Output errors: 8588
  Input errors: 0, Output errors: 8429
  Input errors: 0, Output errors: 8512
  Input errors: 0, Output errors: 8582
  Input errors: 0, Output errors: 8629
Forwarding classes: 16 supported, 4 in use
Egress queues: 8 supported, 4 in use
Queue: 0, Forwarding classes: best-effort
  Queued:
  Transmitted:
    Packets              :                337719
    Bytes                :              74149542
    Tail-dropped packets :                  9669
    RL-dropped packets   :                     0
    RL-dropped bytes     :                     0

 

But on some ports there is almost no traffic. And it happens on all switches

  Input rate     : 0 bps (0 pps)
  Output rate    : 16944 bps (32 pps)
  Input errors: 0, Output errors: 9418

 

I tried to change buffer size, but this is not helped for me.

> show configuration class-of-service    
shared-buffer {
    percent 100;
}

Thank you.

9 REPLIES 9
Junos

Re: Tail-dropped packets EX4200

‎05-16-2019 11:46 AM

Hi,

 

taildropped packets happen because of buffer exhaustion do you have a custom CoS configuration on the device?

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Junos

Re: Tail-dropped packets EX4200

‎05-17-2019 02:52 AM

Hi,

It also can be caused by flow-control protocol. Please, disable flow-control on a link.

Junos

Re: Tail-dropped packets EX4200

[ Edited ]
‎05-19-2019 06:02 PM

You can try giving more bandwidth to best effort queue and see if that improves, check also if other queues are taking up more bandwith than necessary.

 

Another theory is that the switch may be experiencing bottle neck , for example traffic coming from 10gb is going out to 1gb .

 

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Junos

Re: Tail-dropped packets EX4200

‎06-06-2019 04:15 AM

Good Day,

 

Could you please provide next output for the one of the affected interfaces, so we can check QoS settings:

show class-of-service interface ge-0/3/0 comprehensive

 

Thanks!

Junos

Re: Tail-dropped packets EX4200

[ Edited ]
‎09-17-2019 07:05 AM

Good day, I apologize for the long time reply. Thank you all for your responses.

 

On xe-0/0/0 interface:

MAC control frames 0 0
MAC pause frames 0 0

 

And same on all others interfaces

Junos

Re: Tail-dropped packets EX4200

‎09-17-2019 07:07 AM

On problem interface

Input rate : 3847176 bps (387 pps)
Output rate : 584248 bps (371 pps)
Input errors: 0, Output errors: 2145011

 

I see same problem on empty servers where i had rate about 1pps

Junos

Re: Tail-dropped packets EX4200

‎09-17-2019 07:09 AM
> show class-of-service interface ge-0/3/0 comprehensive 
error: command is not valid on the ex4200-48t
> show class-of-service interface ge-0/0/3    
Physical interface: ge-0/0/3, Index: 133
Maximum usable queues: 8, Queues in use: 4
  Scheduler map: <default>, Index: 2
  Congestion-notification: Disabled

  Logical interface: ge-0/0/3.0, Index: 74
Object                  Name                   Type                    Index
Classifier              ieee8021p-untrust      untrust                    16
Junos

Re: Tail-dropped packets EX4200

‎10-29-2019 03:03 AM

Good Day Roman90,

 

I strongly believe there is a configuration issue.

Once interface with very low outgoing traffic is suffering from drops and it is seen on many devices - could be that queue just doesn't have any dedicated bandwidth, according to the configuration.

Could you please provide class-of-service part of the configuration for the review?

 

Thank you!

Junos

Re: Tail-dropped packets EX4200

‎11-01-2019 04:07 AM

Hej

It is hard to address without seeing the CoS config. Can you provide the full CoS config for the problem interface?

#show class-of-service interface

 

Do you only see the problem in BE queue or other queues drop traffic as well?
>show interface <logical interface> queue

 

Also are you monitoring your network? You might be getting bursts in certain times that might be causing the drops. That is why other times it might appear as there is no traffic.

Regards
Oscar