Cisco Cisco Expressway
Call Failures
TLS Calls Fail when Unified CM uses SRV Trunk Destinations
Calls from Unified CM may fail if they use a TLS trunk security profile and SRV trunk destinations (requiring "_sips._
tcp" SRV record lookups in DNS).
tcp" SRV record lookups in DNS).
for up-to-date information regarding the versions of Unified CM
in which this issue has been fixed.
If you need to address one or more Expressway peers you can work around this problem by not using SRV records.
Instead, in the SIP trunk, specify each Expressway Destination Address individually using DNS A-records or static IP
addresses. However, note that these addresses affect the domain portion of the URI received by Expressway from
Unified CM. You may need to set up appropriate transforms on the Expressway to cater for this (see
Instead, in the SIP trunk, specify each Expressway Destination Address individually using DNS A-records or static IP
addresses. However, note that these addresses affect the domain portion of the URI received by Expressway from
Unified CM. You may need to set up appropriate transforms on the Expressway to cater for this (see
).
Encrypted Call Failures
Calls between endpoints registered to Unified CM and endpoints proxied via Expressway will fail if the Unified CM
endpoint requests best effort encryption and the other endpoint does not support encryption. (Unified CM has a
proprietary method for indicating fall back to no encryption - X-cisco-srtp-fallback – which Expressway currently
does not support.)
endpoint requests best effort encryption and the other endpoint does not support encryption. (Unified CM has a
proprietary method for indicating fall back to no encryption - X-cisco-srtp-fallback – which Expressway currently
does not support.)
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Cisco Expressway SIP Trunk to Unified CM Deployment Guide
Appendix 1: Troubleshooting