Hey Vapi team, I have a critical routing request for a BYO SIP Trunk to get our integration working. Context: Our SIP provider in Argentina (IPLAN) has a technical limitation and will only whitelist one of Vapi's outbound signaling IPs. They have currently whitelisted

44.229.228.186

. Problem: As a result, all calls originated from Vapi's other IP (

44.238.177.138

) are being rejected by our provider with a

403 Forbidden

error. This is causing a +50% random call failure rate, which makes the service unusable. Specific Request: Could you please apply a backend routing rule for our credential to ensure that all outbound calls for a specific

credentialId

or account originate exclusively from the whitelisted IP? * Force Outbound IP to:

44.229.228.186

We understand this is not ideal and removes the redundancy benefits of your platform. However, it's a necessary workaround to deal with our provider's limitation and is currently a major blocker for us. Thanks for your help!

Hi Gerónimo, If you're experiencing issues with call forwarding drops, please follow the troubleshooting steps from the [Debug call forwarding drops](https://docs.vapi.ai/phone-calling/transfer-calls/debug-forwarding-drops) guide. Begin by verifying the

endedReason

of the call using the API to see if it shows

"assistant-forwarded-call"

. If it shows successful forwarding but the call still drops, the issue might be with your telephony provider. Check your telephony provider's logs for transfer errors using the

phoneCallProviderId

. Also, ensure your assistant configuration does not include

"phone-call-control"

in

serverMessages

, and

phoneCallProviderBypassEnabled

is set to

false

. If the issue persists across multiple configurations and transfer attempts, consult with your telephony provider for further assistance using their logs, or analyze the SIP signaling if applicable.

The issues are not only related to call forwarding but also with simply calling. The SIP trunk provider restrict the connection to only one IP, instead of the two required by VAPI's documentation. Is there any way to restrict the SIP trunking to only ONE IP?

Unfortunately, it isn’t possible to restrict SIP trunking to a single IP address. For proper SIP signaling and media flow between Vapi and your SIP provider, both of the following IP addresses must be allowlisted:

44.229.228.186/32  
44.238.177.138/32

These IPs are used exclusively for SIP traffic, and both are required for the service to function reliably. If your SIP trunk provider only supports allowlisting one IP address, this may lead to reliability issues or service interruptions, as Vapi’s infrastructure depends on both IPs. We recommend one of the following options: - Work with your SIP provider to allow both IP addresses. - Consider switching to a provider that supports multiple IP allowlists. - Explore other supported SIP providers such as Plivo, Telnyx, or Zadarma.