Issue
When attempting to assign a previously used Elastic SIP Trunk Termination SIP URI domain (e.g., example12345.pstn.twilio.com) to a new trunk or sub-account, you may encounter an error such as:
Error 21248: Trunk Domain already taken
This occurs even if the domain was recently deleted from another (possibly closed) sub-account.
Product
Elastic SIP Trunking
Environment
Twilio Console
Cause
Twilio enforces a retention (cooldown) period for SIP Trunk Termination SIP URI domains after deletion. When a SIP trunk or its domain is deleted even if the sub-account is closed the domain is reserved and cannot be immediately reused. This is a safety and anti-collision measure to prevent accidental reuse or conflicts.
- Sub-account isolation: Each sub-account is treated as a separate entity. Resources deleted from one sub-account cannot be immediately reassigned to another.
- Retention period: The deleted domain remains reserved for up to 30 days before it becomes available for reuse.
Resolution
To resolve this issue:
-
Wait for the Retention Period:
The deleted SIP URI domain will become available for reuse after the retention period (typically up to 30 days). There is no way to expedite this process. -
Use a Different Domain:
For immediate needs, create a new, unique Termination SIP URI domain for your new trunk. You can use a variation of the original domain (e.g., add a number or different word). -
Plan for Domain Reuse:
If you must use the exact same domain, plan for the retention period and avoid deleting domains you may need to reuse soon.
Additional Information
Why does Twilio do this?
The retention period is designed to prevent accidental conflicts and ensure the integrity of SIP trunking resources across all Twilio accounts and sub-accounts.
What if my sub-account is closed?
Even if a sub-account is closed, its resources (including SIP URI domains) are subject to the same retention policy.
Best Practices:
- Use descriptive and unique domain names for each trunk.
- Document domain assignments and sub-account usage to avoid confusion.
- Avoid deleting domains you may need to reuse in the near future.
Related Documentation: