This document describes how to enable Real Time Protocol (RTP) source port validation in order to avoid voice quality problem like crosstalk.
IOS 12.4(6)T or newer versions.
This document is not restricted to specific software and hardware versions.
Caution: The information in this document was created from the devices in a specific lab environment. All of the devices used in this document started with a cleared (default) configuration. If your network is live, ensure that you understand the potential impact of any command.
Public Switch Telephone Network (PSTN) callers experience crosstalk or mixed voice streams in this call flow:
This could happen when the gateway receives an invalid RTP stream destined to the same IP address and port of an active call. The invalid stream has different source IP address and port than the one negotiated via SIP Session Description Protocol (SDP).