Cisco Systems SCCP Inspection Overview, Supporting Cisco IP Phones

11-25
Cisco ASA Series Firewall CLI Configuration Guide
Chapter11 Configuring Inspection for Voice and Video Protocols
Skinny (SCCP) Inspection
•SCCP Inspection Overview, page11-25
•Supporting Cisco IP Phones, page11-25
•Restrictions and Limitations, page11-26
•Configuring a Skinny (SCCP) Inspection Policy Map for Additional Inspection Control, page11-26
•Verifying and Monitoring SIP Inspection, page11-24
SCCP Inspection Overview
Note For specific information about setting up the Phone Proxy on the ASA, which is part of the Cisco Unified
Communications architecture and supports IP phone deployment, see Chapter16, “C onfiguring the
Cisco Phone Proxy.”.
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.
The ASA supports PAT and NAT for SCCP. PAT is necessary if you have more IP phones than global IP
addresses for the IP phones to use. By supporting NAT and PAT of SCCP Signaling packets, Skinny
application inspection ensures that all SCCP signalling and media packets can traverse the ASA.
Normal traffic between Cisco CallManager and Cisco IP Phones uses SCCP and is handled by SCCP
inspection without any special configuration. The ASA also supports DHCP options 150 and 66, which
it accomplishes by sending 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 general operations configuration guide.
Note The ASA supports inspection of traffic from Cisco IP Phones running SCCP protocol version 19 and
earlier.
Supporting Cisco IP Phones
Note For specific information about setting up the Phone Proxy on the ASA, which is part of the Cisco Unified
Communications architecture and supports IP phone deployment, see Chapter16, “C onfiguring the
Cisco Phone Proxy.”
In topologies where Cisco CallManager is located on the higher security interface with respect to the
Cisco IP Phones, if NAT is required for the Cisco CallManager IP address, the mapping must be static
as a Cisco IP Phone requires the Cisco CallManager IP address to be specified explicitly in its
configuration. An static identity entry allows the Cisco CallManager on the higher security interface to
accept registrations from the Cisco IP Phones.
Cisco IP Phones require access to a TFTP server to download the configuration information they need
to connect to the Cisco CallManager server.