My config is not working... BYOC Edge TLS handshake failure during Zendesk migration

Voice & Telephony
1

Having some issues getting my configuration to work… migrating Zendesk digital channels to Genesys Cloud via BYOC Edge. The Edge node logs show a TLS handshake failure with error code 336000732 when connecting to the Genesys Cloud tenant. In Zendesk, we used simple HTTPS endpoints, but here the Edge requires specific certificate chains. Is there a known issue with the latest Edge version 9.0.155 regarding TLS 1.3 compatibility with Genesys Cloud? The connection drops immediately after the initial SYN-ACK. Any advice on adjusting the Edge configuration or checking the tenant-side firewall rules would be appreciated.

2

Yep, this is a known issue with BYOC Edge TLS configurations. The 336000732 error often stems from an incomplete certificate chain rather than TLS version incompatibility.

  • Verify the root and intermediate certificates are included in the trust store
  • Ensure the Edge node clock is synchronized to prevent validation failures
  • Check that the Genesys Cloud tenant certificate matches the expected Common Name
3

This is a classic case of certificate chain truncation rather than a TLS version mismatch, especially since the error code 336000732 points to SSL routines:ssl3_read_bytes:sslv3 alert certificate unknown. The suggestion above about verifying the trust store is spot on, but there’s a specific gotcha with BYOC Edge deployments that often gets missed during migration from simpler setups like Zendesk.

When configuring the genesys-cloud-edge.conf file, the tls.ca-cert parameter must point to a bundle file containing the full chain, not just the root CA. Genesys Cloud’s endpoints often use intermediate certificates that change periodically. If your load generator or the Edge node itself has a stale system CA store, it might validate the root but fail on the intermediate, causing the immediate drop after SYN-ACK.

Here is how to verify and fix the bundle:

  • Download the full certificate chain from the Genesys Cloud tenant URL using OpenSSL:
openssl s_client -connect api.mypurecloud.com:443 -showcerts
  • Extract all certificates (leaf + intermediates) into a single .pem file.
  • Update the Edge configuration:
tls:
ca-cert: /etc/edge/certs/full-chain.pem
verify-peer: true
  • Restart the Edge service to reload the TLS context.

Also, double-check the NTP synchronization on the Edge host. Even a 50-second drift can cause the certificate validity check to fail, resulting in the same handshake error. Since you are migrating from Zendesk, ensure you aren’t relying on the OS default CA store, as BYOC Edge has its own isolated trust model. Run a curl -v test from the Edge server to the tenant API to isolate whether it’s a network-level TLS issue or an application-level config error.

4

The root cause here is the Edge node rejecting the certificate due to a missing intermediate CA in the trust store, not TLS versioning.

ssl3_read_bytes:sslv3 alert certificate unknown

Ensure the full chain is bundled. Zendesk’s simplified HTTPS endpoints often hide this requirement, but BYOC Edge validates strictly. Check the cacerts.jks configuration.