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Cisco ASA Series CLI Configuration Guide
Chapter 1 Configuring Filtering Services
Filtering URLs and FTP Requests with an External Server
Truncating Long HTTP URLs
By default, if a URL exceeds the maximum permitted size, then it is dropped. To avoid this occurrence,
truncate a long URL by entering the following command:
Exempting Traffic from Filtering
To exempt traffic from filtering, enter following command:
Filtering HTTPS URLs
You must identify and enable the URL filtering server before enabling HTTPS filtering.
Note
Websense and Secure Computing Smartfilter currently support HTTPS; older versions of the Secure
Computing SmartFilter (formerly N2H2) do not support HTTPS filtering.
Because HTTPS content is encrypted, the ASA sends the URL lookup without directory and filename
information. When the filtering server approves an HTTPS connection request, the ASA allows the
completion of SSL connection negotiation and allows the reply from the web server to reach the
originating client. If the filtering server denies the request, the ASA prevents the completion of SSL
connection negotiation. The browser displays an error message, such as “The Page or the content cannot
be displayed.”
Note
The ASA does not provide an authentication prompt for HTTPS, so you must authenticate with the ASA
using HTTP or FTP before accessing HTTPS servers.
Command
Purpose
filter url
[
longurl-truncate
|
longurl-deny
|
cgi-truncate
]
Example:
hostname# filter url longurl-truncate
The
longurl-truncate
option causes the ASA to send only the hostname or
IP address portion of the URL for evaluation to the filtering server when
the URL is longer than the maximum length permitted. Use the
longurl-deny
option to deny outbound URL traffic if the URL is longer
than the maximum permitted.
Use the
cgi-truncate
option to truncate CGI URLs to include only the CGI
script location and the script name without any parameters. Many long
HTTP requests are CGI requests. If the parameters list is very long, waiting
and sending the complete CGI request, including the parameter list, can use
up memory resources and affect ASA performance.
Command
Purpose
filter url except
source_ip
source_mask
dest_ip
dest_mask
Example:
hostname(config)# filter url http 0 0 0 0
hostname(config)# filter url except
10.0.2.54 255.255.255.255 0 0
Exempts specific traffic from filtering.
The example shows how to cause all HTTP requests to be forwarded to the
filtering server, except for those from 10.0.2.54.
Summary of Contents for 5505 - ASA Firewall Edition Bundle
Page 28: ...Glossary GL 24 Cisco ASA Series CLI Configuration Guide ...
Page 61: ...P A R T 1 Getting Started with the ASA ...
Page 62: ......
Page 219: ...P A R T 2 Configuring High Availability and Scalability ...
Page 220: ......
Page 403: ...P A R T 2 Configuring Interfaces ...
Page 404: ......
Page 499: ...P A R T 2 Configuring Basic Settings ...
Page 500: ......
Page 533: ...P A R T 2 Configuring Objects and Access Lists ...
Page 534: ......
Page 601: ...P A R T 2 Configuring IP Routing ...
Page 602: ......
Page 745: ...P A R T 2 Configuring Network Address Translation ...
Page 746: ......
Page 845: ...P A R T 2 Configuring AAA Servers and the Local Database ...
Page 846: ......
Page 981: ...P A R T 2 Configuring Access Control ...
Page 982: ......
Page 1061: ...P A R T 2 Configuring Service Policies Using the Modular Policy Framework ...
Page 1062: ......
Page 1093: ...P A R T 2 Configuring Application Inspection ...
Page 1094: ......
Page 1191: ...P A R T 2 Configuring Unified Communications ...
Page 1192: ......
Page 1333: ...P A R T 2 Configuring Connection Settings and QoS ...
Page 1334: ......
Page 1379: ...P A R T 2 Configuring Advanced Network Protection ...
Page 1380: ......
Page 1475: ...P A R T 2 Configuring Modules ...
Page 1476: ......
Page 1549: ...P A R T 2 Configuring VPN ...
Page 1550: ......
Page 1965: ...P A R T 2 Configuring Logging SNMP and Smart Call Home ...
Page 1966: ......
Page 2059: ...P A R T 2 System Administration ...
Page 2060: ......
Page 2098: ...1 8 Cisco ASA Series CLI Configuration Guide Chapter 1 Troubleshooting Viewing the Coredump ...
Page 2099: ...P A R T 2 Reference ...
Page 2100: ......