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QoS configuration on 'router-on-a-stick' with port-channel sub-ints

Joshua Head



i am looking to configure QoS on a customers 4331 ISR. Basic 'router on a stick' setup with a basic Ethernet port-channel configured on three 1G interfaces. Port-channel contains about 10 dot1q sub interfaces.


The policy I'm looking to configure is below:


policy-map pm-queue-out
class cm-class-network
bandwidth remaining percent 2
class cm-class-multimedia5
priority percent 33
class cm-class-multimedia4
bandwidth remaining percent 40
class cm-class-interactive3
bandwidth remaining percent 30
class cm-class-interactive2
bandwidth remaining percent 15
class cm-class-data1
bandwidth remaining percent 8
class class-default
bandwidth remaining percent 5
set dscp default


I've looked through Cisco documentation which all points to configuring aggregated QoS:


The router does not currently have port-channel load-balancing vlan configured which is per-requisite for this.


Is anyone able to point me in the right direction? Do I just apply the inbound marking and outbound policy-maps to the sub-interfaces? If I want to shape traffic on a particular sub-interface is it as simple as applying a child shaping policy to that particular interface?


At the moment I'm at a bit of a dead end.





VIP Guru VIP Guru
VIP Guru
Ethernet port-channel configured on three 1G interfaces.

Most use case always to be Even number for Load-balance - like 2 or 4 or 6 on


Subinterface you can apply as suggested.


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Thanks Balaji, I don't know if that is specific port-channel configuration guidance and I think it may have changed a bit since IOX-XE?


I understand I can apply the shaping policy to the Po1.100 sub-interface but I wanted to understand how that would work in-conjunction with the rest of the member interfaces which only have the child policy configured - if that makes sense.

Joseph W. Doherty
Hall of Fame Master Hall of Fame Master
Hall of Fame Master

Sorry, I'm a bit confused.  Are you just trying to manage the whole Etherchannel as a single interface, manage each subinterface, individually, with some allocated proportion of bandwidth per subinterface or trying to manage individual Etherchannel links?

BTW, managing per Etherchannel link, would be rather unusual.

Managing subinterfaces can be difficult for making effective QoS unless you set aside a fixed proportion of bandwidth for the exclusive, and also always available, use of each subinterface.

For example, you have:

class cm-class-multimedia5
priority percent 33

and you mention having about 10 subinterfaces.  So, is the 33% for all 10 subinterfaces using this kind of traffic, or 33% of each subinterface's allocated bandwidth?

Also BTW, since you're using FQ in many of your classes, you might have twice (or more) classes than you really need.

Often I suggest starting with a CBWFQ model based on:

policy-map model

class real-time !for traffic like VoIP (bearer)
priority percent 35

class foreground
bandwidth remaining percent 81 !light bandwidth usage traffic that really, really needs priorization

class background
bandwidth remaining percent 1 !high bandwidth, low prioity traffic, that is "happy" with left over bandwidth

class class-default !most non-real-time traffic goes here - it's FQ which, often, negates much need for other classes than RT
bandwidth remaining percent 9

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