SIP 423 Interval Too Brief
The handset asked to register for a shorter period than the server allows. It is a straightforward configuration mismatch: raise the registration expiry on the phone to at least the server minimum and it clears.
What SIP 423 Interval Too Brief actually means
The registration expiry requested was too brief, and the response includes a Min-Expires header stating the shortest interval the server will accept. That header makes this one of the few SIP errors that tells you the exact value to configure.
What causes SIP 423 on a business phone system
- The registration interval is set below the server minimumOften the result of someone shortening the interval to fight a NAT timeout and going too far.
- A provisioning template carries a value from another providerPlatforms differ in their minimum, so a template moved between providers can be valid on one and rejected on the other.
How to fix SIP 423
- Read the minimum from the response and use itThe Min-Expires header states the shortest acceptable interval. Set the handset to that value or a little above.
- If you shortened it to fix inbound calls, use keep-alive insteadWhere you need frequent refreshes to hold a NAT pinhole open but the server will not allow it, enable the handset keep-alive option, which maintains the path without re-registering.
Fixing the underlying problem
This page explains the code. These guides walk through the fix in detail.
Questions about SIP 423
How do I fix SIP 423 Interval Too Brief?
Related SIP response codes
Source. SIP 423 Interval Too Brief is defined in RFC 3261 section 21.4.17 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.