Q.850 cause 23 Redirection to new destination
Not a failure. An exchange in the path has decided the call should go to a different number and is asking the previous exchange to re-route it. You will see it as an intermediate leg in a CDR, usually behind a network divert, a non-geographic number translation or a failover arrangement.
What Q.850 cause 23 Redirection to new destination actually means
This is a control mechanism rather than a termination cause. An exchange that concludes the call should be set up to a different called number sends this back to the preceding exchange, effectively saying: do not deliver here, deliver there instead. The call as a whole may then complete perfectly normally at the new destination. Read alongside the following leg in the CDR, not in isolation. RFC 3398 maps it to SIP 410 Gone, which reads oddly for something that is not a failure, but it is the published mapping and gateways will follow it.
This cause is used by a general ISUP protocol mechanism that can be invoked by an exchange that decides that the call should be set up to a different called number. Such an exchange can invoke a redirection mechanism, by use of this cause value, to request a preceding exchange involved in the call to route the call to the new number.
— ITU-T Q.850 section 6.2.7.1.18
The SIP equivalent of Q.850 cause 23
A gateway translating this cause into SIP reports it as SIP 410 Gone. The mapping is defined in RFC 3398 section 7.2.4.1.
What causes Q.850 cause 23 on a business phone system
- A non-geographic number translationAn 0800 or 0300 number is not a destination in itself — it translates to an underlying geographic or trunk number. The redirection step can surface in call records as an intermediate leg with this cause.
- A network-level divertDiverts configured at the carrier rather than on your PBX are applied in the network. The exchange handling the original number instructs the previous one to route to the divert target instead.
- A failover arrangement being invokedDisaster recovery diverts that send calls to mobiles or a second site during an outage work this way. Seeing this cause in bulk is a useful signal that your failover actually triggered.
- A carrier re-routing around a problemWhere an operator needs to move traffic away from an affected destination or platform, redirection to an alternative number can be applied centrally. You will see the effect without having asked for it.
How to fix Q.850 cause 23
- Read the redirected leg before treating it as a faultFind the following record in the CDR and check whether the call connected at the new destination. If it did, nothing is wrong and the redirection did its job.
- Confirm the redirection target is one you intendedCheck the new number against your own divert configuration. An unexpected target means a divert left in place after an incident, or a change nobody recorded.
- Watch for redirection loopsA divert pointing at a number that diverts back produces repeated redirection until a hop counter stops it. If you see the same pair of numbers alternating in the log, break the loop at one end.
- Check how redirected legs appear on your billA redirected call can be charged as two legs depending on the arrangement, particularly where the target is a mobile. Compare the CDR against an invoice line so you know what a failover event actually costs you.
Fixing the underlying problem
This page explains the code. These guides walk through the fix in detail.
Questions about Q.850 cause 23
Is cause 23 a fault?
Will I be charged for a redirected leg?
Related Q.850 cause values
Source. Q.850 cause 23 Redirection to new destination is defined in ITU-T Q.850 section 6.2.7.1.18 and registered in the ITU-T Recommendation Q.850 (10/2018). The causes and fixes above are drawn from our own experience supporting UK business phone systems.