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Configuring QoS on Cisco 3845 router for Polycom Video Conferecing

Dear All,

We have implemented a Polycom Video Conferecing solution at our Head Office. Using this we communicate with other branch offices through WAN (2mbps, MPLS).

The problem is that this WAN link is also used for data. When the traffic is high on the link, the voice and the video quality goes down drastically and we experience connection drops.

At the moment we have configured our Polycom box to communicate at 512kbps speed and we would like to reserve it in our WAN link. In case, video conferencing is not happening we would like it to be utilised by other traffic.

Can we configure QoS on our Cisco 3845 router to do this? I'm not a Cisco expert and have pressures from Management to correct this before the next conference.

I have already googled a fair bit but couldn't find something for me.

Could someone please tell me the exact commands that need to be given on our router to achieve this.

I'll be very thankful for this help.

Best Regards.


Re: Configuring QoS on Cisco 3845 router for Polycom Video Confe


You can use something like the following to guarantee 5122k of bandwidth to your video-conferencing bandwidth but to allow that bandwidth to be used by other traffic when it is not being used for video-conferencing:

class-map VDOConf

match ip dscp af41


policy-map WANPolicy

class VDOConf

bandwidth 512



service-policy output WANPolicy

Note that the above assumes that your video conferencing traffic is being marked to AF41. If that is not the case, you can always match on the IP address of your polycom device using an ACL:

class-map VDOConf

match access-group 101


access-list 101 permit ip .....

Hope that helps - pls rate the post if it does.


New Member

Re: Configuring QoS on Cisco 3845 router for Polycom Video Confe

Thanks Paresh.

I'll test this on our router tonight.

A few more queries:

1. How do I make out whether our traffic is marked as AF41? Sorry, but I don't even know whats this AF41. The Polycom model that we are using is VSX 7000e.

2. Could you pls direct me to some link that tells me more about 'dscp'? I even don't know this.

Thanks once more.

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