48-13
Cisco ASA 5500 Series Configuration Guide using the CLI
Chapter48 Configuring the Cisco Phone Proxy
Phone Proxy Guidelines and Limitations
•General Guidelines and Limitations, page48-13
•Media Termination Address Guidelines and Limitations, page48-14
General Guidelines and Limitations
The phone proxy has the following general limitations:
•Only one phone proxy instance can be configured on the ASA by using the phone-proxy command.
See the command reference for information about the phone-proxy command. See also Creating the
Phone Proxy Instance, page 48-23.
•The phone proxy only supports one Cisco UCM cluster. See Creating the CTL File, page48-18 for
the steps to configure the Cisco UCM cluster for the phone proxy.
•The phone proxy is not supported when the ASA is running in transparent mode or multiple context
mode.
•When a remote IP phone calls an invalid internal or external extension, the phone proxy does not
support playing the annunciator message from the Cisco UCM. Instead, the remote IP phone plays
a fast busy signal instead of the annunciator message "Your call cannot be completed ..." However,
when an internal IP phone dials in invalid extension, the annunciator messages plays "Your call
cannot be completed ..."
•Packets from phones connecting to the phone proxy over a VPN tunnel are not inspected by the ASA
inspection engines.
•The phone proxy does not support IP phones sending Real-Time Control Protocol (RTCP) packets
through the ASA. Disable RTCP packets in the Cisco Unified CM Administration console from the
Phone Configuration page. See your Cisco Unified Communications Manager (CallManager)
documentation for information about setting this configuration option.
•When used with CIPC, the phone proxy does not support end-users resetting their device name in
CIPC (Preferences > Network tab > Use this Device Name field) or Administrators resetting the
device name in Cisco Unified CM Administration console (Device menu > Phone Configuration >
Device Name field). To function with the phone proxy, the CIPC configuration file must be in the
format: SEP<mac_address>.cnf.xml. If the device name does not follow this format
(SEP<mac_address>), CIPC cannot retrieve its configuration file from Cisco UMC via the phone
proxy and CIPC will not function.
•The phone proxy does not support IP phones sending SCCP video messages using Cisco VT
Advantage because SCCP video messages do not support SRTP keys.
•For mixed-mode clusters, the phone proxy does not support the Cisco Unified Call Manager using
TFTP to send encrypted configuration files to IP phones through the ASA.
•Multiple IP phones behind one NAT device must be configured to use the same security mode.
When the phone proxy is configured for a mixed-mode cluster and multiple IP phones are behind
one NAT device and registering through the phone proxy, all the SIP and SCCP IP phones must be
configured as authenticated or encrypted, or all as non-secure on the Unified Call Manager.
For example, if there are four IP phones behind one NAT device where two IP phones are configured
using SIP and two IP phones are configured using SCCP, the following configurations on the Unified
Call Manager are acceptable:
–
Two SIP IP phones: one IP phone in authenticated mode and one in encrypted mode, both in
authenticated mode, or both in encrypted mode
Two SCCP IP phones: one IP phone in authenticated mode and one in encrypted mode, both in
authenticated mode, or both in encrypted mode