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Cisco Security Appliance Command Line Configuration Guide
OL-6721-01
Chapter 21 Applying Application Layer Protocol Inspection
Managing Skinny (SCCP) Inspection
The following is sample output from the show sip command:
hostname# show sip
Total: 2
state Call init, idle 0:00:01
state Active, idle 0:00:06
This sample shows two active SIP sessions on the security appliance (as shown in the Total field). Each
call-id
represents a call.
The first session,
with the call
-id c3943
000-96
0ca-2e
43-228
[email protected].
56.44
, is in the stat
e Call Init
,
which means the session is still in call setup. Call setup is not complete until a final response to the call
has been received. For instance, the caller has already sent the INVITE, and maybe received a 100
Response, but has not yet seen the 200 OK, so the call setup is not complete yet. Any non-1xx response
message is considered a final response. This session has been idle for 1 second.
The second session is in the state Active, in which call setup is complete and the endpoints are
exchanging media. This session has been idle for 6 seconds.
Managing Skinny (SCCP) Inspection
This section describes how to enable SCCP application inspection and change the default port
configuration. This section includes the following topics:
• SCCP Inspection Overview, page 21-47
• Supporting Cisco IP Phones, page 21-48
• Restrictions and Limitations, page 21-48
• Verifying and Monitoring SCCP Inspection, page 21-50
SCCP Inspection Overview
Skinny (SCCP) is a simplified protocol used in VoIP networks. Cisco IP Phones using SCCP can coexist
in an H.323 environment. When used with Cisco CallManager, the SCCP client can interoperate with
H.323 compliant terminals. Application layer functions in the security appliance recognize SCCP
Version 3.3. The functionality of the application layer software ensures that all SCCP signalling and
media packets can traverse the security appliance by providing NAT of the SCCP Signaling packets.
There are 5 versions of the SCCP protocol: 2.4, 3.0.4, 3.1.1, 3.2, and 3.3.2. The security appliance
supports all versions through Version 3.3.2. The security appliance provides both PAT and NAT support
for SCCP. PAT is necessary if you have limited numbers of global IP addresses for use by IP phones.
Normal traffic between the Cisco CallManager and Cisco IP Phones uses SCCP and is handled by SCCP
inspection without any special configuration.The security appliance also supports DHCP options 150
and 66, which allow the security appliance to send the location of a TFTP server to Cisco IP Phones and
other DHCP clients. Cisco IP Phones might also include DHCP option 3 in their requests, which sets the
default route. For more information, see the “Using Cisco IP Phones with a DHCP Server” section in
Chapter 8, “Configuring IP Networking.”
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