McDewey

Webex app unable to register with CUCM via Mobility and Remote Access (MRA) after Call manager, Tomcat and Expressway C certificates renew on mixed-mode deployments. Verification CUCM Call manager and Tomcat certificate are CA signed certificates. 1. CUCM and Expressway deployment runs on mixed-mode (TLS). 2. inspect Expressway-C logs shows "SSL routines:ssl3_read_bytes:tlsv1 alert unknown ca". <#root> 2026-01-29T14:01:16.974-05:00 exp-c traffic_server[2030]: UTCTime="2026-01-29 19:01:16,974" Module HTTPMSG: |GET /CSFmarcoalh.cnf.xml HTTP/1.1 Host: expc.cisco.com:6972 Accept: */* Cookie:<CONCEALED> User-Agent: WebEx/0.0.0.0 TrackingID: fxxxxxxx-86f6-4030-8259-0b768c07723e Client-ip: xxx.xxx.xxx.xxx X-Forwarded-For: xxx.xxx.xxx.xxx, 127.0.0.1 Via: https/1.1 vcs[0fxxxxxx-c853-xxxx-aa16-0a290bf56fc8] (ATS), http/1.1 vcs[5xxxxxxx-7feb-4xxx-9 | 2026-01-29T14:01:16.974-05:00 exp-c traffic_server[2030]:[ET_NET 1]ERROR:SSL connection failed for SSL routines:ssl3_read_bytes:tlsv1 alert unknown ca 3. Solution Export and import certificates between CUCM and Expressway-C to ensure trust relation. Caution: TAC recommend to perform this after hours as this procedure requires services restart. Business Impact is Procedure to complete trust relation between CUCM and Expressway with CA signed certificates 1.