Classifying HTTP Header Fields for NBAR - Cisco Exam 400-251

ACF.

NBAR (Network-Based Application Recognition) is a feature in Cisco IOS that allows the network administrator to identify and classify different types of network traffic based on the application layer protocols being used.

When it comes to HTTP header fields, NBAR can identify and classify several fields in both request and response messages. For request messages, NBAR can classify the following three HTTP header fields:

A. User-Agent: This field contains information about the client application making the HTTP request. It typically includes the name and version of the web browser or other client software being used.

B. Referrer: This field contains the URL of the web page that the user was on before making the current request. This information can be used by web servers to track how users are navigating their site.

C. From: This field contains the email address of the user who submitted a form on the web page. This information can be used to verify the authenticity of form submissions.

The other options listed are not classified by NBAR for HTTP request messages:

D. Content-Encoding: This field is used in HTTP responses to indicate the type of compression used to encode the response body.

E. Location: This field is used in HTTP responses to indicate the URL of a resource that has been moved or redirected.

F. Server: This field is used in HTTP responses to identify the web server software being used to serve the response.

Overall, NBAR can provide granular control over the network traffic by identifying and classifying different types of traffic based on the application layer protocols being used.