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Auto Qos implementation

Hi Friends,


I want to configure auto qos on 4500 series access switches. Can anybody guide what will be to commands to configure auto qos on 4500 series switches? do i also need to configure it on port channel interface which is uplink to core switch?


Core switch is 3850.




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Re: Auto Qos implementation

Hello Wasaq,

you haven't specified the supervisor model and the IOS image running on the device(s).


So I have taken as a reference a QoS configuration guide for IOS XE release 3.7xE aka 15.2.3Ex.


You are using C4500 at access layer. Are they used as stand alone switches or they are grouped in pairs using VSS  feature?


For standalone configuration of autoQoS you can reference the following document


For autoQoS on VSS systems see


Let us follow the document for stand alone switches.

The first note tells that autoQoS cannot be applied to Vlans or etherchannels (port-channels)


>> Auto-QoS cannot be applied to VLANs or EtherChannel interfaces.


However, this does mean that you cannot use auto QoS.

Because after auto QoS has made its job introducing several class-maps and policy-maps and applying them to interfaces you can modify the configuration with manual commands and you can also deal with etherchannels.


To make autoQoS to start you need a global command like

auto qos srnd4


The switch will create all the necessary command lines to configure class-maps, policy-maps and ot appy them to ports .


seven policy-maps are created with the following names



  • There are 7 policy maps that must be defined (5 Input, 2 output)
  • AutoQos-4.0-Input-Policy
  • AutoQos-VoIP-Input-Cos-Policy
  • AutoQos-VoIP-Input-Dscp-Policy
  • AutoQos-4.0-Cisco-Phone-Input-Policy
  • AutoQos-4.0-Output-Policy
  • AutoQos-4.0-Cisco-Softphone-Input-Policy
  • AutoQos-VoIP-Output-Policy

the class-maps can match on CoS bits that are within 802.1Q header on a trunk or they can match on DSCP field in IPV4 header on L2 access ports or L3 routed ports.

Be aware that untagged frames like native Vlan frames on trunk or standard frames received on a L2 access port have no CoS field to match and are treated like frames with CoS = 0.


Auto QoS uses CDP to understand where a Cisco IP phone is connected to a port to decide what policy-maps to use on the port (one for inbound direction one for outbound direction).

You need to have some basic knowledge of QoS to be able to understand what auto QoS does and to make the necessary configurations.

A good starting point for learning can be the QoS FAQ


So Auto QoS is a good tool for you if you are using Cisco IP phones. If you are using third party IP phones some considerations is needed and auto QoS might not be the right tool to use.


Hope to help






Re: Auto Qos implementation

Thank you for reply. Currently we have following IOS 03.09.00.E. So what will be the commands to configure QOS on port channel interfaces?


We also have 4431 routers and Cisco 5545 ASA. So commands for these platforms will be different.



Waqas Arshad


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