RTP NMAP Port-Map Question

[AJ Cruz]

I've set up QoS on a 2911 (15.0.1) router to match RTP audio with the command "match protocol rtp audio." My understanding is this uses NBAR. I'd like to understand what this is matching. Running the "sh ip nbar port-map" command shows no port mapping for RTP.

Is that normal, how do I know what it's actually doing?

Thanks.

[clileikis]

Hi there,

I'm not sure if you've seen the following link:

http://www.cisco.com/en/US/products/ps6616/products_white_paper09186a0080110040.shtml#wp39259

Classification of RTP Payload Types using nBAR

nBAR RTP payload classification not only allows the router to statefully  identify real time audio and video traffic, but it can also  differentiate RTP streams on the basis of specific audio and video  CODECs used. nBAR RTP Payload Classification looks deeper into the RTP  header to classify RTP traffic for voice and video based on the payload  type used (ie: G.711, G.729, and MPEG). The packet is classified as RTP  based on multiple attributes in the RTP header, rather than even UDP  port numbers alone.

HTH,

Chris