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Cisco Security Appliance Command Line Configuration Guide

OL-6721-01

Chapter 17 Applying Filtering Services

Filtering HTTP URLs

Caching Server Addresses

After a user accesses a site, the filtering server can allow the security appliance to cache the server

address for a certain amount of time, as long as every site hosted at the address is in a category that is

permitted at all times. Then, when the user accesses the server again, or if another user accesses the

server, the security appliance does not need to consult the filtering server again.

Note Requests for cached IP addresses are not passed to the filtering server and are not logged. As a result,

this activity does not appear in any reports. You can accumulate Websense run logs before using the

url-cache command.

Use the url-cache command if needed to improve throughput, as follows:

hostname(config)# url-cache dst | src_dst

size

Replace size with a value for the cache size within the range 1 to 128 (KB).

Use the dst keyword to cache entries based on the URL destination address. Select this mode if all users

share the same URL filtering policy on the Websense server.

Use the src_dst keyword to cache entries based on both the source address initiating the URL request as

well as the URL destination address. Select this mode if users do not share the same URL filtering policy

on the Websense server.

Filtering HTTP URLs

This section describes how to configure HTTP filtering with an external filtering server. This section

includes the following topics:

• Configuring HTTP Filtering, page 17-7

• Enabling Filtering of Long HTTP URLs, page 17-8

• Truncating Long HTTP URLs, page 17-8

• Exempting Traffic from Filtering, page 17-8

Configuring HTTP Filtering

You must identify and enable the URL filtering server before enabling HTTP filtering.

When the filtering server approves an HTTP connection request, the security appliance allows the reply

from the web server to reach the originating client. If the filtering server denies the request, the security

appliance redirects the user to a block page, indicating that access was denied.

To enable HTTP filtering, enter the following command:

hostname(config)# filter url [http |

port

]

local_ip

local_mask foreign_ip

foreign_mask

] [allow] [proxy-block]

Replace port with one or more port numbers if a different port than the default port for HTTP (80) is

used. Replace local_ip and local_mask with the IP address and subnet mask of a user or subnetwork

making requests. Replace foreign_ip and foreign_mask with the IP address and subnet mask of a server

or subnetwork responding to requests.

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