Expressway
Mobile and Remote Access
Outside clients discover the edge with _collab-edge._tls. Desk phones keep using _cisco-uds._tcp inside.
- DNS SRV — _collab-edge._tls points at Expressway-E. A public _cisco-uds answer is the wrong record.
- TLS — The edge certificate chain must be trusted by the client.
- Traversal — Expressway-E is the traversal server. Expressway-C is the client.
- REGISTER — CUCM still owns the registration. The edge does not replace the cluster.
Office phones registering while laptops fail means the edge, DNS, or the certificate, not the line CSS. SIP on a new Expressway pair still has to be turned on for MRA.