SIP 487 Request Terminated

What SIP 487 means

The call attempt was cancelled before anyone answered, usually because the caller hung up or because another phone in a ring group picked up first. It fills logs on healthy systems and is very rarely the fault you are looking for.

Client error (4xx)
Sent by The device that was being called
Common

What SIP 487 Request Terminated actually means

A pending request was terminated by a CANCEL from the caller or by the transaction being ended some other way. It records how a call attempt finished, not that anything went wrong, which is why a busy hunt group generates one for every phone that did not answer.

What causes SIP 487 on a business phone system

The caller gave up before it was answeredEvery abandoned call produces a 487 against the ringing extension. This is the majority of them in any normal log.
Another extension in the group answeredWhen a call rings several phones, the first to answer wins and the rest are cancelled with a 487 each. A five-phone hunt group generates four of them on every answered call.
A ring timeout expired and the PBX moved the call onWhen a ring-time limit is reached the system cancels the leg and follows the no-answer rule, which is recorded as a 487 on the extension that was ringing.

How to fix SIP 487

Confirm whether you actually have a problemA 487 alongside answered calls is normal. Only investigate if callers report calls being cut off while ringing, which is a different symptom from a call being cancelled.
Lengthen the ring time if calls are being cut shortWhere the pattern is calls consistently ending after the same short interval, the ring timeout is too aggressive. Twenty to twenty-five seconds suits most businesses.
Investigate the signalling path if it happens at a fixed number of secondsA cancel that always lands at the same point, particularly around thirty seconds, is a signalling problem rather than a caller giving up. Treat it as a dropped-call investigation.

Fixing the underlying problem

This page explains the code. These guides walk through the fix in detail.

Questions about SIP 487

Why is my log full of SIP 487?

Because it is what a cancelled call attempt looks like, and cancelled attempts are normal. Every abandoned call and every unanswered phone in a ring group produces one. A hunt group of five phones logs four on every successfully answered call.

Is SIP 487 the reason my calls are dropping?

Usually not, because a 487 applies to calls that had not yet been answered. If established calls are dropping, look instead at 481 and at session timers. The exception is a 487 that always arrives at the same number of seconds, which points at signalling rather than at a caller hanging up.

Related SIP response codes

Source. SIP 487 Request Terminated is defined in RFC 3261 section 21.4.25 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.

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