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MPLS QoS - SUP720BXL GE Port not supporting Strict Priority & Priority %

Unanswered Question
Nov 20th, 2006
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Hi Sir,

My customer have few C7609s with SUP720 3BXL and running IOS image s72033-advipservicesk9_wan-mz.122-18.SXF6.bin within the MPLS network.

What I experienced is that I can't configured the built-in GE port of the SUP720 for Strict Priority & Priority Percent QoS.

Is there anyone outside there know what is the equivalent or alternative to above mentioned two QoS features ? This is mainly to priortize the voice traffic.

Thanks in advance.


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Overall Rating: 5 (1 ratings)
romccallum Tue, 11/21/2006 - 03:59
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This port is mainly a layer 2 port mate. You are into the mls qos settings for this. You cannot do "fancy" qos on any "free" port that cisoc give you on the 7600.

swaroop.potdar Tue, 11/21/2006 - 06:32
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As rom pointed out you cannot do fancy queuing or for that matter the CBWFQ on the GiG ports in a 76K.

You will have to use the default DSCP PREC COS maps to map the incoming values to the internal COS values of the 76K platform.

And then forward these internal COS values to the Priority Queue. And Accordingly assign the weights/percentages to the Queues like you would want to do in fancy queuing.

If you have further quesitons on this do feel free to respond.



r.hew Wed, 11/22/2006 - 17:32
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Hi Swaroop,

First of all I would like to thank you on information shared and agreed we can do on other GiG ports in 76K except the "SUP720 built-in GiG ports".

In my case, below is what the message I got when I tried to do what you have suggested;


policy-map setEXP


police cir percent 10 conform-action transmit exceed-action transmit violate-action drop


class GOLD

bandwidth percent 30

class SILVER

bandwidth percent 25

class class-default

bandwidth percent 1

PECORE01(config-if)#service-policy output setEXP

police percent command is not supported in output direction for this interface

Configuration failed on:


Note that the GiG port 5/2 is the GiG port in SUP720.

Awaiting your response. Thank you.

romccallum Thu, 11/23/2006 - 01:34
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Hi mate. You are trying to do exactly what myself and swaroop are telling you you cannot do on 7600 free lan ports. You have to use the cos values. Check how many queues you are allowed it will be something like

1p/4q = 4 queues in total with 1 priority queue.

The qos that you need to do is mls qos or better known as cos based queuing.

This is the megga gotcha that everyone gets stung on with these 7600's.

swaroop.potdar Thu, 11/23/2006 - 01:58
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When I had mentioned that you need to use Internal COS value and direct them to the appropriate queues (These are hardware Queues), And yes its true as robert pointed :-) , that everyone does get stung now a days with the QOS on 7600 using PFC.

The difference between L2 Lan ports on Line Cards and SUP is the number of Standard Hardware Queues it supports, as by default all the L2 port have 1 priority queue.

So normally the SUP7203BXL supports 1P2Q2T on the Egress and a WRR scheduler for placing traffic

onto the queues. Cannot explain much on the thread but am trying to put as much info as possible.

So to configure this queuing you should proceed as below, Not using the MQC.

i) Enabling the MLS on the 7600 chassis.

ii) Configuring Trust Boundary on all Interfaces.

iii) Directing Traffic into the appropriate Egress Queue.

iv) Defining Queue Bandwidth Limits.


swaroop.potdar Thu, 11/23/2006 - 01:59
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The below has been recommended for a customer using 7600 in the

Core with GiGs as normal core facing links.

The implementation goes as below:

i) Enabling the MLS on the 7600 chassis.


mls qos


ii) Configuring Trust Boundary on all Interfaces.


interface GigabitEthernet1/1

mls qos trust


<--By default the Trust Command trusts the incoming DSCP/TOS.

When the ports are configured with the Trust Boundary as given above,

all incoming packets are mapped into Initial Internal DSCP values.

These values are used purely as a reference MAP for Internal QOS

processing on the 7600.

Internal DSCP Output COS

DSCP 0 7 COS 0

DSCP 8 15 COS 1

DSCP 16 23 COS 2

DSCP 24 31 COS 3

DSCP 32 39 COS 4

DSCP 40 47 COS 5

DSCP 48 55 COS 6

DSCP 56 63 COS 7

This deafault mapping can be modified by modifying the DSCP-COS MAP

within the MLS QOS. The the default mapping are as per standards,

and hence it is not recommended to change the mapping.

iii) Directing Traffic into the appropriate Egress Queue.

Once the incoming traffic is mapped to the Initial Internal DSCP,

and the same gets mapped to the Output COS, these values need to

be directed to the appropriate Queues for the desired QOS behavior

on the MPLS EXP packets.


interface x/x

wrr-queue cos-map

priority-queue cos-map


For Eg:


interface gigabitethernet 1/10

wrr-queue cos-map 2 threshold 2 0

wrr-queue cos-map 3 threshold 2 1 2

wrr-queue cos-map 4 threshold 2 3 4

priority-queue cos-map 1 5 6 7


iv) Defining Queue Bandwidth Limits.

After directing the COS to appropriate queues and then assigning them

to appropriate drop threshold values, it is required to define the

bandwidth allocation per queue. This can be done as below.


!<-- To Set minimum assured bandwidth to COS Queue 1,2 & 3

Use the Bandwdith Percentage command as below.


interface GigabitEthernet 1/1

wrr-queue bandwidth percent !


<--Total of Queue Weights should be =100%


To evenly distribute the available bandwidth during congestion for

all the 4 queues, it is required to set the Queue Scheduling Weights

between all the four Queues. This is done by assigning the queues

weights which are used during WRR scheduling.

!<--Set the Queue-Limit Weights of WRR Scheduling as below


interface GigabitEthernet 1/1

wrr-queue queue-limit

priority-queue queue-limit xx


!<--For Example:


interface GigabitEthernet 1/1

wrr-queue queue-limit 25 20 22

priority-queue queue-limit 33


!<-- The example above does a Queue scheduling for Queue 1 for 25% of BW,

Queue 2 for 20% and Queue 3 for 22 % and Priority Queue has 33 %.


To conclude if you want to use the conventional MQC based toggles,

you will need to use FlexWans with WAN ports or OSM's. Where you can

apply the conventional MQC based toggles.

FOr all the LAN ports in 7600 only hardware queues are supported which

can be controlled using MLS, the difference between SUP and Module based

LAN ports is withing the Scheduling alogirthms supported, the Egress and Ingress

buffers, and the number of queues and drop thresholds available.

For Reference use this link:





Policy Map Class Command Restrictions

PFC QoS does not support these policy map class commands:





?set qos-group


dankennedy Fri, 03/30/2007 - 05:38
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Swaroop, if the ports are in a no switchport mode, is it possible to use conventional MQC based toggles if the RSP720 is used?


richard.troman Fri, 03/30/2007 - 05:47
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hi, the router is really a switch, so think in switch qos. You can configure a priority-queue on the interface. As with LAN qos the qos will not take affect until congestion.

The priority queue will use the various map tables to work out if its a voice parket or not. its the internal mappings that are important, as its these that are used on egress to a port from the internals of the box.

dankennedy Fri, 03/30/2007 - 06:01
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Ok but does the use of only switch Qos (CoS) reduce the scalability when providing QoS solutions to customers with different requirements?

Really getting the impression that the 7600 is not really a router, more of a switch with routing features?

Just seems like the 7600 is a little weak in the QoS area?

My problem is i need to use 2 PE routers connected by 2 gigabit ethernet connections. Each PE will also have Customer connections into it. With the 7600 i have limited Qos and no LNS functions for L2TP/PPP.

If i use a 7200VXRs i can do MQC QoS between PE routers, and have LNS functions.However i have to use a switch (maybe 4948 or 3750) connected to the 7200 in trunk mode.

What do you think is the best way to go?


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