> For the complete documentation index, see [llms.txt](https://help.security.gallagher.com/knowledge-hub/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://help.security.gallagher.com/knowledge-hub/products/cc-hardware/controllers/controller-6000/troubleshoot/controller-6000-controller-drops-offli.md).

# Controller Drops Offline Immediately After Coming Online

Resolve a Controller 6000 that drops offline immediately after its first connection.

**Symptom:** After initial connection, the controller shows online (or online with a purple question mark), then goes offline and stays offline.

***

## Cause 1 - Invalid Server IP cached when services started

A possible scenario is that when the FT Services started, an invalid IP Address was resolved which is then sent to the controller (for example, no network connection at services-start time).

Typical invalid addresses:

* `127.0.0.1` (loopback)
* `169.254.x.x` (APIPA, Windows auto-assigned)

If you are also trying to upgrade or downgrade the controller, when it reboots it will use the incorrect IP Address.

### How to fix

1. Check what the controller has stored for the Server IP via the **TCP Sender** page (web-browse the controller, see [Testing Controller Connections](/knowledge-hub/products/cc-hardware/controllers/controller-6000/troubleshoot/controller-6000-testing-controller-connections.md)).
2. Confirm that the Server has the correct IP Address (ping the host name).
3. **Restart the FT Services.**
4. Perform a **Push Configuration** to the controllers (from the controller's right-click context menu).

***

## Cause 2 - IPv6 enabled but not filled out

Another issue: the **IPv6 option may have been enabled, but the IPv6 address is not filled out**.

This usually happens when the controller has had its IP address assigned by web browsing. The controller will work fine, but **rebooting or power cycling will result in the controller never coming back online to the server**.

### Diagnosis

1. Web-browse to the controller (`{IP}/debug.`).
2. Examine the **TCP Sender** page. The IP address of the server will be missing in the node table.
3. Go to the directory listing and examine the `Main.ini` file. You should see something like:

```ini
[Begin]
[BertType]
Type=62
GroverType=0
Version=vGR8.10b143
ElmoVersion=8.10.1113
[Network]
DHCP=0
DNSLookupPeriod=120
ID=3
IP1=
Port1=1072
FixedServerIP=1
S=21236
```

The `IP1=` entry has no IP address because the IP address for the server has been removed. The controller is set to use an IPv6 address that was never configured on the server.

### Fix

1. Uncheck the **IPv6 option** in the Controller properties.
2. Push config to the controller.
3. The controller will come online.

***

🔗 **Related**

* [Bringing online and networking](/knowledge-hub/products/cc-hardware/controllers/controller-6000/configure/controller-6000-bringing-online-and-ne.md). The wider bringing-online workflow.
* [Trouble Bringing a Controller Online for the First Time](/knowledge-hub/products/cc-hardware/controllers/controller-6000/troubleshoot/controller-6000-trouble-bringing-online-first-time.md). First-connection issues.
* [Testing Controller Connections](/knowledge-hub/products/cc-hardware/controllers/controller-6000/troubleshoot/controller-6000-testing-controller-connections.md). Diagnostic tools for the TCP Sender page.


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