Output queue errors on cisco 2811 ATM1/0 interfaces

[nandushankar]

Hi

We are facing output queue problems on our ATM interfaces. A lot of output queue errors are been shown as below. Need help in solving this issue.

Cisco 2811 -> ATM Link -> <-ATM Link <- Cisco 3945 Routers.

Cisco 2811 Version is 124-15.T9.bin

Cisco 3945 Version is SPA.150-1.M1.bin

Cisco 2811 Output Errors

sh int atm1/0 | incl errors|Input

  Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 11348

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

     0 output errors, 0 collisions, 0 interface resets

Cisco 3945 Output Errors

sh int atm1/0 | incl errors|Input

  Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 313

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

     0 output errors, 0 collisions, 0 interface resets

Regards

Nandu

[Joseph W. Doherty]

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Posting

Your "errors" are the output drops?

What their percentage relative to number of packets offered?  (I.e. what's a lot?)

If the issue is output drops due to congestion, if transient congestion, they might be reduced by allocating larger output queues.

[nathanaelminesso]

Hi Nandu

Can you copy paste the following outputs?

Show int | inc xload

Show run | inc (affected interfaces, you can delete the ip addresses)

Show policy map interface (affected interfaces

Show int sum

Show int stat

+

Show controllers E1 0/0/0 or whatever controller you have

Regards,

Nate

[Giuseppe Larosa]

Hello Nandu,

but what are the interface counters ?

You should always compare the errors to the total number of packets sent out the interface in order to understand if the issue is real or not.

From time to time the queue can fill with bursts of traffic so some drops are natural as the ATM interface is slower then the internal LAN interface.

if you have 11348 drops over several tens of  millions of sent packets you can live with this.

if the ratio output drops / packet sent is 10% this is not acceptable and should be investigated further.

By the way, have you configured any QoS feature on these devices like shaping and/or queueing on the ATM interfaces?

By using QoS you can provide better treatment to packets belonging to important applications for your business

Hope to help

Giuseppe