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Cisco ASA Series CLI Configuration Guide
Chapter 1 Configuring Inspection for Voice and Video Protocols
SIP Inspection
Note
Only the Chat feature is currently supported. Whiteboard, File Transfer, and Application Sharing are not
supported. RTC Client 5.0 is not supported.
SIP inspection translates the SIP text-based messages, recalculates the content length for the SDP
portion of the message, and recalculates the packet length and checksum. It dynamically opens media
connections for ports specified in the SDP portion of the SIP message as address/ports on which the
endpoint should listen.
SIP inspection has a database with indices CALL_ID/FROM/TO from the SIP payload. These indices
identify the call, the source, and the destination. This database contains the media addresses and media
ports found in the SDP media information fields and the media type. There can be multiple media
addresses and ports for a session. The ASA opens RTP/RTCP connections between the two endpoints
using these media addresses/ports.
The well-known port 5060 must be used on the initial call setup (INVITE) message; however, subsequent
messages may not have this port number. The SIP inspection engine opens signaling connection
pinholes, and marks these connections as SIP connections. This is done for the messages to reach the
SIP application and be translated.
As a call is set up, the SIP session is in the “transient” state until the media address and media port is
received from the called endpoint in a Response message indicating the RTP port the called endpoint
listens on. If there is a failure to receive the response messages within one minute, the signaling
connection is torn down.
Once the final handshake is made, the call state is moved to active and the
signaling connection remains
until a BYE message is received.
If an inside endpoint initiates a call to an outside endpoint, a media hole is opened to the outside interface
to allow RTP/RTCP UDP packets to flow to the inside endpoint media address and media port specified
in the INVITE message from the inside endpoint. Unsolicited RTP/RTCP UDP packets to an inside
interface does not traverse the ASA, unless the ASA
configuration specifically allows it.
Configuring a SIP Inspection Policy Map for Additional Inspection
Control
To specify actions when a message violates a parameter, create a SIP inspection policy map. You can
then apply the inspection policy map when you enable SIP inspection.
To create a SIP inspection policy map, perform the following steps:
Step 1
(Optional) Add one or more regular expressions for use in traffic matching commands according to the
“Configuring Regular Expressions” section on page 1-14
. See the types of text you can match in the
match
commands described in
Step 2
(Optional) Create one or more regular expression class maps to group regular expressions according to
the
“Creating a Regular Expression Class Map” section on page 1-17
Step 3
(Optional) Create a SIP inspection class map by performing the following steps.
A class map groups multiple traffic matches. Traffic must match
all
of the
match
commands to match
the class map. You can alternatively identify
match
commands directly in the policy map. The difference
between creating a class map and defining the traffic match directly in the inspection policy map is that
the class map lets you create more complex match criteria, and you can reuse class maps.
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: ......