> For the complete documentation index, see [llms.txt](https://v5cookbook.denovolab.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://v5cookbook.denovolab.com/troubleshoot/sip-switch-is-down.md).

# SIP Switch is Down

How do you tell if Class 4 is down?

![](https://2160858555-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-MYRPW5mw1EmjxhpuA4p%2F-MYTcu0T0t5IPKZjJmcI%2F-MYTdGjk8BQ5pUpgqqS4%2Fimage.png?alt=media\&token=ba0812e4-662f-4892-83f7-f93572ba2fc2)

If you see the class4 switch is disconnected, then you can restart it.

Here is the command to restart Class 4 softswitch if it is down:

```
systemctl start dnl_softswitch
```

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