We use Vapi as SIP extension n228TC203 (BYO phone number 7fc055ad-160b-4a61-a6c6-250dd3e663be) behind KalliopePBX (Asterisk). Blind transfer to sip:202@reg.kloudpbx.it is intermittent with 100% correlation to Vapi egress IP: 019e0359-3569-733f-a2d2-bdf1d96e0e0d egress 44.229.228.186 ✅ transfer ok 019e0362-2824-7226-b0b8-270c234b94c6 egress 34.213.129.25 ❌ call drops 019e0363-0edf-799d-a332-d518fefea491 egress 44.229.228.186 ✅ transfer ok PBX provider packet capture confirms: REFER seen only from 44.229.228.186, not seen from 34.213.129.25. Need BYO SIP trunk egress affinity/pinning (single region/IP) or a supported workaround + ETA. Also Vapi pcapUrl is empty (24 bytes) for failing call, blocking SIP debug. @User can infra please advise ETA? #1211483291191083018

Action Required: Ensure your PBX/firewall allowlists both Vapi SIP signaling IPs:

44.229.228.186/32
44.238.177.138/32

Missing one can cause intermittent transfer failures, as Vapi may use either IP for signaling on any call. Please confirm with your PBX provider that both are explicitly allowed for SIP traffic ([see documentation](https://docs.vapi.ai/advanced/sip/sip-networking)). Source: - [SIP networking and firewall configuration](https://docs.vapi.ai/advanced/sip/sip-networking)

Thanks — we’ll confirm both IPs are allowlisted with our PBX provider. However our failing calls show call.customer.sipUri egress as 34.213.129.25 (example callId 019e0362-...). Can you clarify how that maps to the documented signaling IPs 44.229.228.186 / 44.238.177.138? Also, even with both IPs allowlisted, our PBX (Asterisk/Kalliope) behaves like single-active-registration per AOR; if Vapi can register/signaling from multiple IPs, REFER may be dropped when the call lands on the non-registered egress. Do you support egress affinity/pinning for BYO SIP trunks?