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Inbound Calling on sip trunk returning 503
# support
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v
Action Required: Make sure your SIP provider has whitelisted all required Vapi signaling IPs for inbound calls. Missing IPs can cause 503 errors like the one you’re seeing. Add these to your provider’s allowlist:
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44.229.228.186/32
44.238.177.138/32
After updating, retest your inbound call. This should resolve the 503 error if it was due to incomplete IP whitelisting. For more details, see the [Vapi SIP trunk documentation](https://docs.vapi.ai/advanced/sip/sip-trunk). Source: - [Vapi SIP Trunk Documentation](https://docs.vapi.ai/advanced/sip/sip-trunk)
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It was all whitelisted
@User
@User can someone help me out here?
c
Hi Ω ΣκοτάδιΣεληνόφωτο Ω, For assistance with configuring your SIP Trunks with Plivo, you can follow these steps: Configuring Plivo SIP for Inbound Trunks 1. **Plivo Console Setup**: - Navigate to 
Zentrunk (SIP) → Inbound Trunks → Origination URI → Create New IP URI
. - Fill the 
URI
with 
sip.vapi.ai;transport=udp
. - Create an Inbound Trunk and attach the number purchased. 2. **Vapi Setup**: - Post to the API to create a new 
byo-sip-trunk
credential:
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bash
     curl -X POST https://api.vapi.ai/credential \
     -H "Content-Type: application/json" \
     -H "Authorization: Bearer YOUR_VAPI_PRIVATE_API_KEY" \
     -d '{ "provider": "byo-sip-trunk", "name": "PLIVO Inbound Trunk", "type": "inbound" }'
- Then attach your Plivo phone number with the SIP credential:
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bash
     curl -X POST https://api.vapi.ai/phone-number \
     -H "Content-Type: application/json" \
     -H "Authorization: Bearer YOUR_VAPI_PRIVATE_API_KEY" \
     -d '{ "provider": "byo-phone-number", "name": "PLIVO SIP Inbound Number", "number": "1833684XXXX", "numberE164CheckEnabled": false, "credentialId": "YOUR_CREDENTIAL_ID" }'
Common Issues - Ensure that Plivo numbers are associated correctly with Vapi configurations. - Verify IP Allowlist: 44.229.228.186/32, 44.238.177.138/32 for SIP traffic. - Remember only G.711 µ-law and A-law codecs are supported, avoid others. For more detailed steps, check our [Plivo SIP Integration guide](https://docs.vapi.ai/advanced/sip/plivo).
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This isnt a plivo setup
I get the error which i sent in the images
Could you please take a look at them?
Hello @User ??
c
Hi Ω ΣκοτάδιΣεληνόφωτο Ω, To troubleshoot issues with inbound SIP trunks, please follow these steps: 1. **Network Configuration**: Ensure the IP addresses 
44.229.228.186/32
and 
44.238.177.138/32
are allowlisted for SIP traffic between Vapi and your SIP provider. This is essential for proper signaling and media flow [see details here](https://docs.vapi.ai/advanced/sip/sip-trunk). 2. **Plivo Configuration**: - Verify your Plivo inbound trunk is set up correctly. Make sure the Origination URI is set as 
sip.vapi.ai;transport=udp
. - Ensure your phone number in Plivo is configured to use the correct Zentrunk inbound trunk. [See Plivo configuration guide](https://docs.vapi.ai/advanced/sip/plivo). 3. **Vapi Configuration**: - Confirm that your Vapi dashboard is set up with the correct API key and that your Plivo phone number is associated with the correct SIP trunk credential. - Check any error logs for specific 
endedReason
values such as 
call.ringing.sip-inbound-caller-hungup-before-call-connect
or 
call.ringing.error-sip-inbound-call-failed-to-connect
, which can indicate what might be going wrong with the call connection [more information here](https://docs.vapi.ai/changelog/2025/6/7). These steps should help ensure your inbound SIP trunks are configured correctly. If you encounter specific error codes from the logs, they can provide more insight into the issue.
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