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Community Member

Policy map - stop class going over x mbps?

Hi team,

I am having some trouble with my WAN link. We have replication data traversing the WAN from our head office to our DR site constantly. With this traffic marked I can see that even though the bandwidth percent is at 30%, it continually rises to up around 85-90% of the link.

I understand that this is how the command should work, however it seems that it is causing issues becasue other traffic that is prioritised higher is not getting through fast enough even though it is a small amount of traffic.

What I want is for the SAN_REPLICATION data class map to stay at a certain mbps value and not exceed it. I understand that the commands do only use the rest of the traffic when there is nothing competing but for some reason having this use so much bandwidth is severely impacting the TCC_DIRECT and BSADB1 traffic, which are both time sensitive apps.

class-map match-all TCC_DIRECT

description DATA_TO_TCC_MELB

match  dscp af32

class-map match-all SAN_REPLICATION

description DATA_FROM_VLAN_5_(SAN)

match  dscp cs1

class-map match-all VIDEO_QoS

description DATA_FROM_VLAN_7_(VIDEO)

match  dscp cs5

class-map match-all BSADB1

description DATA_FROM_BSADB1

match  dscp cs3



policy-map QoS_POLICY


bandwidth percent 30

class VIDEO_QoS

  priority percent 10

class BSADB1

  bandwidth percent 7


  bandwidth percent 7

class class-default


policy-map SHAPE_TRAFFIC_20Mbps

class class-default

  shape average 20000000

  service-policy QoS_POLICY

You can see in the below command how much of the 20mbps it uses

sh policy-map interface fa0/1


  Service-policy output: SHAPE_TRAFFIC_20Mbps

    Class-map: class-default (match-any)

      3519814138 packets, 3485395070405 bytes

      30 second offered rate 20166000 bps, drop rate 238000 bps

      Match: any

      Traffic Shaping

           Target/Average   Byte   Sustain   Excess    Interval  Increment

             Rate           Limit  bits/int  bits/int  (ms)      (bytes)

         20000000/20000000  125000 500000    500000    25        62500

        Adapt  Queue     Packets   Bytes     Packets   Bytes     Shaping

        Active Depth                         Delayed   Delayed   Active

        -      3         3509502603 42797116  867244093 2966129398 yes

      Service-policy : QoS_POLICY

        Class-map: SAN_REPLICATION (match-all)

          2282323520 packets, 2910036574815 bytes

          30 second offered rate 18455000 bps, drop rate 156000 bps

          Match:  dscp cs1 (8)


            Output Queue: Conversation 265

            Bandwidth 30 (%)

            Bandwidth 6000 (kbps)Max Threshold 64 (packets)

            (pkts matched/bytes matched) 631886976/922640865641

        (depth/total drops/no-buffer drops) 0/3600346/285

        Class-map: VIDEO_QoS (match-all)

          19120396 packets, 9693435746 bytes

          30 second offered rate 0 bps, drop rate 0 bps

          Match:  dscp cs5 (40)


            Strict Priority

            Output Queue: Conversation 264

            Bandwidth 10 (%)

            Bandwidth 2000 (kbps) Burst 50000 (Bytes)

            (pkts matched/bytes matched) 3326730/1543851666

            (total drops/bytes drops) 3525/4315479

        Class-map: BSADB1 (match-all)

          521509844 packets, 203628804995 bytes

          30 second offered rate 1310000 bps, drop rate 11000 bps

          Match:  dscp cs3 (24)


            Output Queue: Conversation 266

            Bandwidth 7 (%)

            Bandwidth 1400 (kbps)Max Threshold 64 (packets)

            (pkts matched/bytes matched) 135182018/42882862506

        (depth/total drops/no-buffer drops) 3/2446771/83

        Class-map: TCC_DIRECT (match-all)

          1689609 packets, 435893589 bytes

          30 second offered rate 51000 bps, drop rate 0 bps

          Match:  dscp af32 (28)


            Output Queue: Conversation 267

            Bandwidth 7 (%)

            Bandwidth 1400 (kbps)Max Threshold 64 (packets)

            (pkts matched/bytes matched) 764569/176799062

        (depth/total drops/no-buffer drops) 0/0/0

        Class-map: class-default (match-any)

          695170913 packets, 361600541180 bytes

          30 second offered rate 346000 bps, drop rate 67000 bps

          Match: any


            Flow Based Fair Queueing

            Maximum Number of Hashed Queues 256

        (total queued/total drops/no-buffer drops) 0/4260811/143

Any help would be great, thank you.

Community Member

Policy map - stop class going over x mbps?

Remember to set up the bandwidth command on the interface!

Super Bronze

Policy map - stop class going over x mbps?


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You might embed a policer in the SAN_REPLICATION class, but I would first suggest setting your shaper's Tc to about 10ms, if larger, and reducing the SAN_REPLICATION class bandwidth reservation.  (Normally everyone thinks of class bandwidth as bandwidth allowances, but it also impacts scheduler class packet selection too.  If the other classes will leave sufficient bandwidth, you might even try just 1% for SAN_REPLICATION.)

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