FreeSWITCH: Hangup sofia/external/74951234567 [CS_EXCHANGE_MEDIA] [INCOMPATIBLE_DESTINATION]

What it means

The call ended because the two sides could not agree on media: no common codec or unsupported SDP (Q.850 cause 88, SIP 488).

Why it happens

• The provider supports only PCMA, the phone offers only G.722/OPUS (or the other way round).
• SRTP required on one side and not offered on the other.
• outbound-codec-prefs or inherit_codec settings narrow the list.

How to fix it

1. Add PCMA/PCMU to codec-prefs of the profile and gateway.
2. Match SRTP settings (rtp_secure_media) on both legs.
3. Compare the offer and answer in the SDP analyzer.

Useful tools

SDP analyzer · Q.850 cause 88

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