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Cisco ASA Series CLI Configuration Guide
Chapter 1 Configuring Inspection for Voice and Video Protocols
Skinny (SCCP) Inspection
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
Chapter 1, “Configuring the Cisco
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.
When the Cisco IP Phones are on a lower security interface compared to the TFTP server, you must use
an access list to connect to the protected TFTP server on UDP port 69. While you do need a static entry
for the TFTP server, this does not have to be an identity static entry. When using NAT, an identity static
entry maps to the same IP address. When using PAT, it maps to the same IP address and port.
When the Cisco IP Phones are on a
higher
security interface compared to the TFTP server and
Cisco CallManager, no access list or static entry is required to allow the Cisco IP Phones to initiate the
connection.
Restrictions and Limitations
The following are some of the known issues and limitations when using SCCP application inspection:
•
PAT does not work with configurations containing the
alias
command.
•
Outside NAT or PAT is
not
supported.
If the address of an internal Cisco CallManager is configured for NAT or PAT to a different IP
address or port, registrations for external Cisco IP Phones fail because the ASA currently does not
support NAT or PAT for the file content transferred over TFTP.
Although the ASA supports NAT of TFTP messages and opens a pinhole for the TFTP file, the ASA
cannot translate the Cisco CallManager IP address and port embedded in the Cisco IP Phone
configuration files that are transferred by TFTP during phone registration.
•
The ASA supports stateful failover of SCCP calls except for calls that are in the middle of call setup.
•
When the ASA is running in transparent firewall mode, it blocks SCCP voice traffic because
pinholes are not opened for the connection. Displaying debugging messages for SCCP inspection
indicate that RTP and RTCP channels are not open. This limication affects communication between
IP Phones and the Unified Communications Manager.
To workaround this limitation, perform one of the following actions to open secondary connections:
–
(Preferred) Install static route entries for IP Phones or convert to routed mode.
–
Configure static ARP entries for IP Phones
Example:
UC Manager---IP Phone 1---Inside ASA (Transparent)---Outside ASA---IP Phone 2
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 ...
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