Cisco ASA 5505 - Manual (Page 803)

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Cisco ASA 5500 Series Configuration Guide using the CLI
Chapter 39 Configuring Filtering Services
Filtering URLs and FTP Requests with an External Server
Note URL caching will only work if the version of the URL server software from the URL server vendor
supports it.
Although ASA performance is less affected when using an external server, you might notice longer
access times to websites or FTP servers when the filtering server is remote from the ASA.
When filtering is enabled and a request for content is directed through the ASA, the request is sent to
the content server and to the filtering server at the same time. If the filtering server allows the connection,
the ASA forwards the response from the content server to the originating client. If the filtering server
denies the connection, the ASA drops the response and sends a message or return code indicating that
the connection was not successful.
If user authentication is enabled on the ASA, then the ASA also sends the username to the filtering
server. The filtering server can use user-specific filtering settings or provide enhanced reporting about
usage.
Licensing Requirements for URL Filtering
The following table shows the licensing requirements for URL filtering:
Guidelines and Limitations for URL Filtering
This section includes the guidelines and limitations for this feature.
Context Mode Guidelines
Supported in single and multiple context mode.
Firewall Mode Guidelines
Supported in routed and transparent firewall mode.
IPv6 Guidelines
Does not support IPv6.
Table 39-4 Licensing Requirements
Model License Requirement
All models Base License.