SIP 403 Forbidden on BYOC Trunk Failover despite Valid Credentials

Administration
1

Having some issues getting my configuration to work as expected during our nightly failover drills. We manage 15 BYOC trunks across APAC, and the primary carrier is stable. However, when we force a failover to the secondary carrier (a local Singapore provider) via the outbound routing policy, the calls drop immediately.

SIP 403 Forbidden: Authentication Required

The primary trunk registers fine with 200 OK. The secondary trunk also shows ‘Registered’ in the Trunk settings UI. Yet, any call routed to it fails with a 403. I have verified the SIP credentials in the Genesys Cloud admin panel match exactly what the carrier provided, including the realm. I even regenerated the secret on the carrier side and updated it in GC, but the result is identical.

We are using the standard SIP trunk connector. The error logs in the call detail record (CDR) show the INVITE is sent, but the 403 comes back before any media negotiation. Is there a specific header mismatch or digest authentication quirk with certain carriers that causes this? The primary carrier uses standard digest auth, but this secondary one might be stricter. Any insights on debugging the SIP signaling payload for the failed 403 response would be appreciated.

2

The simplest way to resolve this is to verify that your sip_domains array explicitly aligns with the tenant’s regional configuration, as suggested above. While the previous post nailed the core issue regarding credential mismatches, there is a secondary layer often overlooked in multi-region setups. Ensure the secondary trunk’s outbound proxy settings are not inadvertently routing through a primary region’s edge node that lacks the specific BYOC authorization scope for that Singapore provider.

Check the allowed_origins in your trunk configuration. If it defaults to *, it might bypass the specific auth headers required by local carriers. Restricting it to the actual carrier IPs often forces the correct auth handshake. See the WFM-Trunk integration docs here: https://developer.genesys.cloud/api-docs/wfm/trunk-auth.

This usually resolves the 403 immediately after a trunk restart. Also, double-check that the shift schedule for the agents using these trunks doesn’t have conflicting timezone offsets affecting the credential refresh token, though that is a rare edge case.