44-16
Cisco ASA 5500 Series Configuration Guide using the CLI
Chapter44 Configuring Inspection for Voice and Video Protocols
RTSP Inspection
Using RealPlayer
When using RealPlayer, it is important to properly configure transport mode. For the ASA, add an
access-list command from the server to the client or vice versa. For RealPlayer, change transport mode
by clicking Options>Preferences>Tra nspo rt>RTS P Settings.
If using TCP mode on the RealPlayer, select the Use TCP to Connect to Server and Attempt to use
TCP for all content check boxes. On the ASA, there is no need to configure the inspection engine.
If using UDP mode on the RealPlayer, select the Use TCP to Connect to Server and Attempt to use
UDP for static content check boxes, and for live content not available via Multicast. On the ASA, add
an inspect rtsp port command.
Restrictions and Limitations
The following restrictions apply to the RSTP inspection.
•The ASA does not support multicast RTSP or RTSP messages over UDP.
•The ASA does not have the ability to recognize HTTP cloaking where RTSP messages are hidden
in the HTTP messages.
•The ASA cannot perform NAT on RTSP messages because the embedded IP addresses are contained
in the SDP files as part of HTTP or RTSP messages. Packets could be fragmented and ASA cannot
perform NAT on fragmented packets.
•With Cisco IP/TV, the number of translates the ASA performs on the SDP part of the message is
proportional to the number of program listings in the Content Manager (each program listing can
have at least six embedded IP addresses).
•You can configure NAT for Apple QuickTime 4 or RealPlayer. Cisco IP/TV only works with NAT
if the Viewer and Content Manager are on the outside network and the server is on the inside
network.
Configuring an RTSP Inspection Policy Map for Additional Inspection Control
To specify actions when a message violates a parameter, create an RTSP inspection policy map. You can
then apply the inspection policy map when you enable RTSP inspection.
To create an RTSP inspection policy map, perform the following steps:
Step1 (Optional) Add one or more regular expressions for use in traffic matching commands according to the
“Configuring Regular Expressions” section on page13-12. See the types of text you can match in the
match commands described in Step 3.
Step2 (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 13-15.
Step3 (Optional) Create an RTSP 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.