> 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-7000-and-7000-sdc/configure/controller-7000-dynamic-dns.md).

# Dynamic DNS

Configure Controller 7000 DNS failover to reconnect to a backup Command Centre server.

The DNS setting on a controller allows Domain Name Servers (DNS) to be used in **disaster recovery situations**, particularly where backup servers reside on different subnets.

This configuration also applies to Controller 7000 SDC.

***

#### What is the DNS setting on a controller for?

1. If DNS is configured on the controller and the server stops responding for **at least 10 minutes**, the controllers start querying the specified DNS servers in order, attempting to connect to the listed IP address.
2. If the controller cannot connect to any listed DNS server, it continuously cycles through the DNS servers.
3. Once it connects to a server, it stays connected to that server until the connection is lost for 10 minutes, at which point it queries the DNS servers again, starting with the primary server.

#### How does a controller fail over to a backup server using DNS?

* The controller looks for the server **CNAME** on the DNS server.
* The CNAME points to the **A record**, which contains the server's IP address.
* The A record must be **manually updated** to point to the new server IP address (unless the site has Dynamic DNS configured) before controllers can find the backup server.

> ⚠️ **Important:** The backup server must use the **same FQDN** as the production server.

***

## Configuration notes

DNS is configured on the controller's network settings in Command Centre. There is no special "Dynamic DNS" mode to enable separately. The behavior described above is automatic once DNS servers are specified in the controller's configuration.

> **Troubleshooting:** If controllers are not failing over to the backup server, verify:
>
> 1. The DNS A record for the server FQDN has been updated to point to the backup server's IP address.
> 2. The backup server is using the same FQDN as the production server.
> 3. The controller's configured DNS server(s) are reachable from the controller's subnet.
> 4. The 10-minute timeout has elapsed before the failover is expected.

***

🔗 **Related**

* [Use Cases for Use Different IP Addresses for Server](/knowledge-hub/products/cc-hardware/controllers/controller-7000-and-7000-sdc/configure/controller-7000-use-cases-for-use-diff.md). Another way to point a controller at a different server IP.
* [Bringing Online and Networking](/knowledge-hub/products/cc-hardware/controllers/controller-7000-and-7000-sdc/configure/controller-7000-bringing-online-and-ne.md). How a controller resolves and connects to its server.
* [Testing Controller Connections](/knowledge-hub/products/cc-hardware/controllers/controller-7000-and-7000-sdc/troubleshoot/controller-7000-testing-controller-con.md). Confirm the controller can reach the backup server.


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