Calls drop after a few seconds

Symptom

A call connects and then disconnects by itself:

• after the same number of seconds every time (often around half a minute);
• at random points during the call; or
• before it’s answered, when the caller is being routed through your call flow.

Note when the call drops and whether it’s every call. A drop at the same point every time usually points to the network or call flow, not the line.

On a free trial?

Trial calls to and from outside numbers end after 1 minute. If your calls always drop at about one minute, that’s the trial limit, not a fault. Verify your identity and activate your account to remove it. See Your free trial.

Quick checks

1. Same time every call? Time a few test calls. A fixed time points to the router (causes 1 and 2).
2. Before or after answering? If callers are cut off before anyone answers, check the call flow first (cause 4).
3. One site or everywhere? Try the Webphone on a mobile hotspot. If calls stay up, your office network is the cause.

Likely causes and fixes

1. SIP ALG on the router

Many routers have a SIP ALG feature that rewrites call signalling. It often breaks the messages that confirm a call is connected, so both sides hang up after a set time.

Fix: turn off SIP ALG (it may be called “SIP helper”, “SIP passthrough” or “SIP fixup”) in the router, then restart the router and the phones. See Network requirements.

2. The router forgets the call (NAT timeout)

Routers keep track of each connection for a limited time. If the phone or router lets that record expire, signalling during the call can no longer reach the phone and the call drops.

Fix:

• Make the phone send keep-alive messages more often. On a Yealink phone, go to Account › Advanced and set Keep Alive Type to Options and Keep Alive Interval (Seconds) to 30. See Device offline for the related registration setting.
• Make sure the phone’s transport matches the Transport protocol shown in the device’s SIP credentials in PBX › Devices.

3. Session timers

During a long call, phones and servers check every so often that the call is still active (a session timer). If that check fails, for example because the router blocks it, the call ends at the same point every time, often after several minutes.

Fix: apply fixes 1 and 2 first. If calls still drop at a fixed time, note the exact duration and contact support.

4. An unconnected path in the call flow

If a call reaches a path that isn’t connected on the PBX canvas, the call ends. For example:

• a Voice menu whose Timeout or Invalid path isn’t connected;
• a Queue whose Maximum waiting time exceeded path isn’t connected;
• a Ring group or User whose No answer path isn’t connected.

Fix: connect every path callers can take, for example to Voicemail, and click Apply configuration.

5. Unstable internet or Wi-Fi

Short internet outages and weak Wi-Fi drop calls at random points.

Fix: use a wired connection for desk phones and computers, and see Poor call quality.

On the nbn, see nbn connection issues.

6. The balance ran out

A call in progress isn’t cut off when a prepaid balance runs out: it finishes normally. But new calls fail straight away until you top up, which can look like a dropped call. See Account suspended or low balance.

When to contact support

Create a support ticket with:

• the dates and times of dropped calls (with your time zone) and the numbers involved;
• how long each call lasted before it dropped, and whether it was before or after answering;
• the device type, and your router make and model;
• whether it happens on another network, such as a mobile hotspot.