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Frequent Contributor


Hi Everyone,

We are replacing our PRIs with SIP trunks on ISR 4431. The provider offers SIP trunks over MPLS. My question is, do we need to consider any QoS on the CUBE? If so, would that be possible to have a configuration example?



Jitender Bhandari
Cisco Employee

Hi MK,

See below for helps.

(Rate if it helps)


Thanks guys, your help is very much appreciated.


Philip D'Ath

If the MPLS circuit only has VoIP traffic and nothing else on it then you don't need to worry.  There is nothing to re-prioritise.

Hi Philip,

I just talked to the service provider and found out that there's no dedicated MPLS circuit for VoIP traffic . Would you happen to have a configuration sample for QoS on CUBE to share?



Yo MK,

does your CUBE actually connect to the sip provider through a dedicated physical link, or does your existing WAN/MPLS connection that carries data carry the additional SIP and RTP to your provider?

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Frequent Contributor

Hi Dennis,

There's no dedicated circuit for VoIP traffic. The SIP Trunks will be carried overs existing MPLS connection. I am looking for a QoS configuration for the CUBE.



Hi MK,

When you say that your provider is providing SIP trunk over MPLS, do you mean that the connectivity between your CUBE and ITSP gateway is over MPLS cloud? This is unusual.

If this is the case, you need agree with your ITSP about the markings for voice and signaling. I am assuming that you will be sending voip traffic only (regardless whether your provider is carrying data traffic over the MPLS cloud). If you are sending voip traffic only out of this link, you don't need to perform and policing/queuing. You just need to mark traffic as agreed with your provider.

Thanks Mohammad,

Next week, we have a meeting with the provider about all these détails and I will have more info to share but for now what I know is that there's no didicated circuit for VoIP. 

I guess my question is:

Is there any senario that we need to consider implemention QoS in CUBE? If yes, can you please share a configuration sample?



Hi MK,

I don't think your QoS will be relevant as the MPLS circuit for provider use mainly and not something you requested. You need to know the codec to be used and the number of concurrent calls along with L2 protocol (ethernet, frame-relay, etc). This will give you the required bandwidth.

From CUBE qos, you need to mark traffic only as requested by your provider


It's pretty common for a carrier to offer a SIP circuit over and existing MPLS cloud. I have this set up for several of my clients.  And QoS definitely needs to be taken into consideration so your 'data' traffic doesn't walk all over your VOIP traffic.  To do this all you need to do is apply a QoS policy on your edge router where you connect to the MPLS circuit (which may or may not be your CUBE).   Below is a sample QOS policy, where XXX is the amount, in Kb, of RTP voice stream that you need.  You will need to make sure your carrier honors your EF marked traffic up to this XXX amount.  For example if you have a 10Mb MPLS circuit and your carrier allows 10% of that to be EF prioritized traffic, then your XXX would be 1000 ( or 1 Mb).

class-map match-any Voice-RTP

match dscp ef

class-map match-any Signaling

match dscp af31

 match dscp cs3

policy-map LLQ

class Voice-RTP

  priority XXX

class Signaling

  bandwidth YYY

class class-default


  random-detect dscp-based

interface GigabitEthernet0/1

description ***MPLS handoff***

ip address

bandwidth 10000

service-policy output LLQ

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