CTIQBE
The Telephony Application Programming Interface (TAPI) and Java Telephony Application
Programming Interface (JTAPI) are used by many Cisco VoIP applications. Cisco TAPI
Service Provider (TSP) uses CTIQBE to communicate with Cisco CallManager. CTIQBE
protocol is disabled by default. The inspect ctiqbe command enables CTIQBE protocol
inspection that supports NAT, PAT, and bidirectional NAT. This enables Cisco IP SoftPhone
Application Inspection Support for Voice over IP 593
and other Cisco TAPI/JTAPI applications to work successfully with Cisco CallManager for
call setup across the firewall. Additionally, CTIQBE is used as a signaling protocol by older
Cisco IP phones and the newer Cisco IP Communicator to perform call setup with the Cisco
CallManager.
There are, however, instances when CTIQBE application inspection has limits or does not
support some configuration types. CTIQBE application inspection does not support the
following:
■ Stateful failover of CTIQBE calls
■ CTIQBE messages fragmented in multiple TCP packets
■ Configurations that use the alias command
The following summarizes special considerations when using CTIQBE application
inspection in specific scenarios:
■ If two Cisco IP SoftPhones are registered with different Cisco CallManagers, which are
connected to different interfaces of a Security Appliance, calls between these two phones
will fail.
■ When Cisco CallManager is located on the higher-security interface compared to Cisco
IP SoftPhones, if NAT or outside NAT is required for the Cisco CallManager IP address,
the mapping must be static because Cisco IP SoftPhone requires the Cisco CallManager
IP address to be specified explicitly in its Cisco TSP configuration on the PC.
■ When using PAT or outside PAT, if the Cisco CallManager IP address is to be translated,
its TCP port 2748 must be statically mapped to the same port of the PAT (interface)
address for Cisco IP SoftPhone registrations to succeed. The CTIQBE listening port (TCP
2748) is fixed and is not user-configurable on Cisco CallManager, Cisco IP SoftPhone,
or Cisco TSP.