# FQDN SIP connection

**URL:** https://community.livekit.io/t/fqdn-sip-connection/1150
**Category:** Telephony
**Tags:** sip-trunking
**Created:** [May 17, 2026, 12:10pm UTC](https://community.livekit.io/t/fqdn-sip-connection/1150 "2026-05-17T12:10:29Z")
**Posts on this page:** 3
**Page:** 1

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### Author: ![ZeroDay-TheChosenNeo](https://sea1.discourse-cdn.com/flex001/user_avatar/community.livekit.io/zeroday-thechosenneo/32/1367_2.png) [@ZeroDay-TheChosenNeo](https://community.livekit.io/u/ZeroDay-TheChosenNeo)
#### Post date: [May 17, 2026, 12:10pm UTC](https://community.livekit.io/t/fqdn-sip-connection/1150/1 "2026-05-17T12:10:29Z")

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I have an FQDN SIP connection pointing to LiveKit Cloud (`3cetozcjms6.sip.livekit.cloud`, port 5060). Inbound calls to my Greek number +302318510764 are immediately rejected with Q.850 cause code 1 (0 seconds duration). The FQDN resolves correctly and ports 5060/5061 are reachable.

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### Author: ![Muhammad\_Usman\_Bashir](https://sea1.discourse-cdn.com/flex001/user_avatar/community.livekit.io/muhammad_usman_bashir/32/1149_2.png) [@Muhammad\_Usman\_Bashir](https://community.livekit.io/u/Muhammad_Usman_Bashir)
#### Post date: [May 17, 2026, 1:33pm UTC](https://community.livekit.io/t/fqdn-sip-connection/1150/2 "2026-05-17T13:33:10Z")

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@ZeroDay-TheChosenNeo, `Q.850` cause code 1 (“unallocated number”) with 0s duration on a reachable trunk is almost always a number-format mismatch between what your carrier sends and what’s in the LiveKit inbound trunk’s numbers array.

Per the inbound trunk docs, numbers is stored as E.164 with the leading + (e.g., “+302318510764”). If the carrier delivers `302318510764`, `00302318510764`, or a national-format variant, LK can’t match it and rejects with cause 1.

Three checks:

- Dump the trunk config: `lk sip inbound list`. Confirm `+302318510764` is in the numbers array exactly, with the leading +.
- Inspect the carrier’s `INVITE`: SIP trace or carrier-side log of the To: URI. Many EU carriers default to national or `00-prefix` format.
- Sidestep matching: set `numbers: []` (accept any) and gate with `allowed_addresses` IP `allowlist` or `username/password`. Useful while you confirm the carrier’s format.

Same root cause pattern @CWilson diagnosed on a Telnyx trunk earlier this month: format mismatch beats trunk reachability on cause code 1.

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### Author: ![CWilson](https://sea1.discourse-cdn.com/flex001/user_avatar/community.livekit.io/cwilson/32/135_2.png) [@CWilson](https://community.livekit.io/u/CWilson)
#### Post date: [May 18, 2026, 4:14pm UTC](https://community.livekit.io/t/fqdn-sip-connection/1150/3 "2026-05-18T16:14:03Z")

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> [@ZeroDay-TheChosenNeo](#):
>
> I have an FQDN SIP connection pointing to LiveKit Cloud

I can see your call is reaching your agent. I think there is something wrong with your agent code like it is getting an error. Check your agent logs for answers. Make sure it is calling “connect”