Noob to QoS. I have a few questions.

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Sep 8th, 2009

I am looking for the simplest way to configure QoS on my Routers. What I have is a hub and spoke network configuration. I have a 2651 XM Router at the head end and 2811's at all the spokes, the 2651 is running c2600-ipbasek9-mz.124.17.bin, and the 2811's are running c2800nm-advsecurityk9-mz.124.3g.bin.

What is the simplest way to configure QoS on the routers? Is the auto QoS the best bet? I am looking to get our VoIP traffic priority. We are running a non Cisco VoIP system in a Telrad PBX. We are using the TVSe server to be exact.

From what I have seen the 2811's are okay on the software, but the 2651 will need updated. So question number two is what version of software should I install on the 2651 Router? I was thinking c2600-ipvoicek9mz.124-25b.bin.

I guess this is a good place to start with the questions.

Any help would be appreciated.



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Edison Ortiz Tue, 09/08/2009 - 07:08


You may find my suggestion(s) a little complex but they will provide a scalable end-to-end QoS solution.

1) You need to mark at ingress in your switches. I'm not sure what type of switches you are using but you can classify the Telrad PBX traffic and IP Phone traffic as they enter the network. The classification will be performed by matching on the UDP ports and apply DSCP EF to those packets. If the IP Phones are sending EF, all you need to do is trust the port.

2) Once the VoIP packets are classified, you can match these packets at the WAN routers and select the type of congestion management (LLQ or CBWFQ), policing or shaping.

For voice, I recommend assigning LLQ and not to exceed 33% of the interface bandwidth.

As far as IOS, the one mentioned above should be able to support the current QoS standards in the 2600.

I recommend reading the following links:

The QoS documentation on 12.4

The QoS SRND 3.3

and the newly updated QoS SRND 4.0




ddevecka Tue, 09/08/2009 - 07:15

I am running a mixture of 3Com, Linksys, and Cisco switches. I will read through what you sent and proceed from that point.



Edison Ortiz Tue, 09/08/2009 - 07:23

Hi Dan,

You have a lot of work in front of you if you decide to deploy an end-to-end QoS design. A multi-vendor QoS, specially in switches, can be quite painful.

Based on the network you have at hand, I recommend applying the QoS just on the routers.

You can create ACLs matching on the type of UDP traffic coming from the VoIP devices and classify them on the router;

access-list 101 permit udp [VoiP subnet] range [udp-ports] [Remote VoIP subnet] range [udp-ports]

class-map match-any VoIP

match access-group 101

policy-map VoIP

class VoIP

priority xx

set ip dscp ef

policy-map QoS_For_WAN

class class-default

shape average xxxxx

service-policy VoIP

interface ....

description WAN Facing Interface

service-policy output QoS_For_WAN




Joseph W. Doherty Tue, 09/08/2009 - 08:32

What kind of hub and spoke? (I.e., LL, frame-relay, ATM, VPN, etc.) Such can impact what you might need to do for QoS.

Similar to Edison, you might be fine using CBWFQ with VoIP bearer placed in LLQ and everthing else within class-default FQ.


class-map match-axx VoIP

match . . .

policy-map aSample

class VoIP

!you can adjust % as needed - Cisco recommends not to exceed 33%

prioity percent 30

!there's an implict class-default and FQ; when not defined


!however it defaults to FIFO in HQF so

class class-default


interface ?

!wan connected/facing

service-policy output aSample

Re: 2nd quesiton

Don't think you need a Voice feature set unless the router is actually working with VoIP directly (e.g. PBX), i.e. not just moving VoIP packets.

ddevecka Tue, 09/08/2009 - 09:00

The 2 main spokes are PtP T's using multilink PPP.

We set a trunk group up on the PBX to push intercampus traffice down the T's to save a few bucks.


Joseph W. Doherty Tue, 09/08/2009 - 09:11

Alright then, policy sample I provided would be the place to start.

NB: There are issues using VoIP on low bandwidth links (with data traffic) and it's possible to fragment packets across MLPPP, but neither, I think, should be an issue for your with multple bundled T1s. The shaper that Edison showed, would be needed if you end-to-end path has less bandwith then the interface hand off; again shouldn't be an issue for you.

ddevecka Tue, 09/08/2009 - 09:25

Also what about AutoQoS? Or is this just something for Cisco Phone systems?

Thanks again for all the input.



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