Pause Input and Pause Output Errors on Router Internet facing Interface

[sreeraj.murali]

Hi,

Please find the below ouput frow the show interface command from the Router Outside Interface connected to Internet Service Provider.

 0 watchdog, 0 multicast, 122 pause input
     1474107 packets output, 352324562 bytes, 0 underruns
     0 output errors, 0 collisions, 0 interface resets
     0 unknown protocol drops
     0 babbles, 0 late collision, 0 deferred
     0 lost carrier, 0 no carrier, 220198 pause output

Is this a cause of concern ? I have GRE Tunnel running over this Internet interface, passing Voice traffic as well. Please advice.

Thanks & Regards

Sreeraj

[Palani Mohan]

Sreeraj

No two devices  in a network path are matching each other. In other words, there will be mismatches. Given this, you can expect some amount of pause frames. Pause frames are basically layer-2 flow control mechanism, indicating congestion.

Partial outputs will lead to speculation. Speculations are generally not helpful. Please consider sharing the complete output (show tech preferably).

Kind regards ... Palani

[sreeraj.murali]

Hi,

I am attaching the show tech support output from the VPN Router. Please check and suggest. I am also seeing input errors on the interface.

Thanks & Regards

Sreeraj

[Palani Mohan]

Hi Sreeraj

The router is underpowered to handle the load. Take a look at your CPU history. You are reaching high 90s, consistently and repeatedly.

The time/date when show tech was taken is not the busiest time and so, I am not getting a clean picture on the utilization.

Take a look at http://miercom.com/pdf/reports/20091001.pdf

While this does not cover 2921 itself, we know that 2921 is positioned between 2911 and 2951. So, you can expect a t'put around 35-60Mbps, depending on the pktSize. If your contracted WAN bandwidth is higher than this, then please consider upgrading the routing platform that is designed to meet the contracted WAN bandwidth.

Kind regards ... Palani

[sreeraj.murali]

Hi,

Ok. Thanks.

I am attaching the show tech output for yesterday evening, when we had the link maximum utilized. Please check, if you are still seeing the CPU utilization in the show tech output.

Thanks

Sreeraj

[Palani Mohan]

Hi Sreeraj

As you may have noticed, CPU was NOT high when the show tech was taken.

Recommend the following changes be made:

!
process cpu threshold type total rising 90 interval 10 falling 60 interval 10
process cpu threshold type interrupt rising 60 interval 10 falling 40 interval 10
process cpu threshold type process rising 75 interval 10 falling 60 interval 10
!
line con 0
 exec prompt timestamp
!
line vty 0 4
 exec prompt timestamp
!
int gi 0/0
 ip flow ingress
!
int gi 0/1

 ip flow ingress
!
int tun 0
 ip flow ingress
!
logging buffer 1000000
!

These cmds trigger a syslog when the CPU rises and falls. The syslog message sample would look something like:

%SYS-1-CPURISINGTHRESHOLD: Threshold: Total CPU
Utilization(Total/Intr): 90%/85%, Top 3 processes(Pid/Util):  61/2%, 125/1%, 2/0%

From this message, we can be informed about:
Total CPU utilization
Amount of CPU spent servicing interrupts
Top 3 processes PID# with # CPU utilized by these processes
How long the condition lasted

Most important: Are you actively troubleshooting any performance issues? Are any of your users complaining slow performance? What is the contracted bandwidth with your WAN provider?

Wait for 1 business week to complete. Then, share the show log. This will tell us a pattern of when the CPU load is high. Based on what we find here, we can make progress.

Kind regards ... Palani

[sreeraj.murali]

Sure, I will share the log.

At the moment, is the PAUSE INPUT and PAUSE OUTPUT a cause of concern ?

Please suggest.

[Palani Mohan]

Hi Sreeraj

Yes, it is definitely a cause for concern. That is the reason for recommending you to continue investigation.

Please don't clear counters. Just issue show cmd twice and look at the delta if you want to know how quickly the counters are changing.

Kind regards .... Palani

[sreeraj.murali]

Hi,

I did had a major issue today. I am attaching the show tech. Could you please analyse the log and suggest.

Thanks & Regards

Sreeraj

[sreeraj.murali]

Hi Palani, Hope you have got a chance to look at the "show tech" shared.

Also, the Internet Leased Line bandwidth delivered by Service provider is 10 Mbps.

Kindly check and suggest.

[Palani Mohan]

Hi Sreeraj

Unfortunately, the show tech was taken when the CPU was normal:-( Assuming you made the config changes mentioned earlier, please send us show log. Let's see what it tells us.

Kind regards .... Palani