Posts Tagged ‘nbar’
NBAR protocol classification feature has long supported enhanced HTTP URL matching features. However, Cisco documentation site never provided a detailed description of the pattern language used for URL matching; neither has it explained how the engine matches client/server data streams. In this post we will give an overview of how NBAR works with URL filtering.
We will arrange this post in a FAQ manner as follows.
Can we use NBAR on the gateway router to prevent internal users from watching video streams from any video web site (like Youtube.com)?
Yes, NBAR can be used to apply application based filters such as blocking youtube.com traffic. To accomplish this we can categorize traffic based on the HTTP hostname. Next we will create a policy-map that matches the youtube.com class and drops the traffic. Lastly the policy is applied outbound to the Internet. Syntax-wise this would read:
R1# class-map match-all YOUTUBE match protocol http host "*youtube.com*" ! policy-map DROP_YOUTUBE class YOUTUBE drop ! interface FastEthernet0/0 description TO INTERNET service-policy output DROP_YOUTUBE
NBAR for HTTP can also be used to match based on URL string or IANA MIME type. For more information see: