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2005
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15
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QoS question

Hi,

Have this Gig interface directly connected to a 10Mb link to the ISP.

GigabitEthernet0/0 is up, line protocol is up
  Hardware is MV96340 Ethernet, address is 0025.45f2.09a0 (bia 0025.45f2.09a0)
  Internet address is x.x.x.x/30
  MTU 1500 bytes, BW 10000 Kbit/sec, DLY 100 usec,
     reliability 255/255, txload 75/255, rxload 61/255

There's QoS configured outbound for a TCP application to provide 30% of interface bandwidth. 

interface GigabitEthernet0/0
bandwidth 10000
service-policy output ARCUS-QOS

Which values do I have to see on the txload/rxload in the interface to have QoS kick in?

    Class-map: TRANSACTIONAL (match-all)
      23896 packets, 4597078 bytes
      5 minute offered rate 12000 bps, drop rate 0 bps
      Match: access-group 160
      Priority: 30% (3000 kbps), burst bytes 75000, b/w exceed drops: 0

When is the interface considered congested?

Federico.

19 Replies 19

Hi Federico,

I don't think that's qos problem. Can you check the output of show interface stats, do you see lot process switched? Only process switched traffic will be put on input queue, I would try to find out whether  this type traffic has been process switched.

Tune the buffer might also help, but I would check whether the traffic has been process switched first.

http://www.cisco.com/en/US/customer/products/hw/routers/ps133/products_tech_note09186a00800a7b80.shtml

HTH,

Lei Tian

#sh int stats
GigabitEthernet0/0
          Switching path    Pkts In   Chars In   Pkts Out  Chars Out
               Processor     337000   31567901     274833   29361560
             Route cache   23608968 2487058066   29071572 3694126557
                   Total   23945968 2518625967   29346405 3723488117

Seems there are some packets process-switched, but CEF is enabled on the interface.

I'll check the buffer link and let you know thanks.

Federico.

Hi Federico,

It is normal to have some traffic been process switched, like control plane traffic. The transit traffic should be cef switched unless it cannot be cef switched. For example, packet with ttl=1, packet with destination to the device, fragment packets need to be reassemble...

I think you can configure a ACL match the traffic having problem, and run debug ip packet for this ACL. The output can tell you whether this type of traffic is process switched.

Regards,

Lei Tian

Hi Lei,

please can you indicate a configuration example or any procedure/command (using the Control Plane Policy) to check which packets will be process switches ?

Thanks in advace

Roberto Taccon

Hi Roberto,

show cef not-cef-switched

(http://www.cisco.com/en/US/docs/ios/12_2/switch/command/reference/xrfscmd4.html#wp1082741)

might be a little helpfil here showing the reasons why some packets were not CEF-switched.

BR,

Milan

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