SIP 604 Does Not Exist Anywhere
What SIP 604 means
The number does not exist anywhere, not just on the system that answered. That usually means the number itself is wrong: an unallocated range, a missing or extra digit, or a wrong country code.
What SIP 604 Does Not Exist Anywhere actually means
The server has authoritative information that the user does not exist anywhere in the network. It is a stronger statement than a 404, which only speaks for one domain, so it points at the number being dialled rather than at your routing.
What causes SIP 604 on a business phone system
- The number is unallocated or has been ceasedNumbers that were never issued, or that have been given up, do not exist to route to. Old marketing lists and stale internal directories are full of them.
- A digit is missing or extraA transposed or dropped digit commonly lands in an unallocated range, producing this rather than a wrong number.
- The international format is wrongA missing country code, or a national trunk zero left in an international number, makes an address nobody owns.
How to fix SIP 604
- Re-check the number against a second sourceConfirm it from the recipient website or a recent email rather than from the record that produced the failure.
- Check the international dialling formatFor overseas numbers, use the country code and drop the leading national zero. This single error accounts for a large share of 604s on international calls.
- Check the dial plan is not altering the numberA rule that adds or strips a digit can turn a valid number into an unallocated one, so take a trace and read what actually left.
Fixing the underlying problem
This page explains the code. These guides walk through the fix in detail.
Questions about SIP 604
What is the difference between SIP 604 and SIP 404?
A 404 means the number does not exist on the system that answered, so it might exist elsewhere and your routing may be at fault. A 604 means no system anywhere recognises it, which points at the number itself being wrong or unallocated.
Related SIP response codes
Source. SIP 604 Does Not Exist Anywhere is defined in RFC 3261 section 21.6.3 and registered in the IANA SIP Parameters — Response Codes. The causes and fixes above are drawn from our own experience supporting UK business phone systems.