> 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/cloud-services/onelink/communication.md).

# Communication

Understand OneLink traffic flow, local controller communication, and firewall allowlisting.

All controller-to-cloud communication is on **port 443**. The **Controller Registration Service** is part of the Gallagher Cloud, not an external system.

![OneLink topology - the Local CC Server and a 7000 Controller each connect to the Gallagher Cloud over TCP 443, with the Controller Registration Service above](https://328339335-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2F6bM8WhlBE9BYizPWJaPN%2Fuploads%2Fgit-blob-a6b8e4b1701fc28b355b8a603ff9dcea5e6c12a5%2FSECHUB-onelink-communication-01.png?alt=media)

## Registration sequence

1. The controller starts with **DIP switches 2 and 7 on** and reaches the Controller Registration Service.
2. The service talks to the Gallagher Cloud and identifies the destination Command Centre server.
3. The service tells the controller how to talk to the Gallagher Cloud.
4. The controller and the Command Centre server communicate through the Gallagher Cloud.

![OneLink registration flow via the Controller Registration Service](https://328339335-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2F6bM8WhlBE9BYizPWJaPN%2Fuploads%2Fgit-blob-cf4edba00bfa953eb582437a042ff15f2f3164bc%2FSECHUB-onelink-communication-02.png?alt=media)

## Local network path

Each controller connects to the cloud on **443**. Controllers on the same LAN talk to each other on **1072**.

![OneLink local-network communication path between controllers on port 1072](https://328339335-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2F6bM8WhlBE9BYizPWJaPN%2Fuploads%2Fgit-blob-cbee35db928ac8a28709607401de9c689d2c53f5%2FSECHUB-onelink-communication-03.png?alt=media)

## Networking requirements (firewall allowlist)

> These are public Gallagher cloud service endpoints. Allowlist them on the site firewall.

| Endpoint                               | DNS                                                     | IP addresses                     |
| -------------------------------------- | ------------------------------------------------------- | -------------------------------- |
| Australian Command Centre Cloud        | `commandcentre-ap-southeast-2.security.gallagher.cloud` | `52.62.211.7`, `54.79.91.203`    |
| Australian Gallagher Gateway Region    | `commandcentre-api-au.security.gallagher.cloud`         | `3.106.1.6`, `3.106.100.112`     |
| United States Gallagher Gateway Region | `commandcentre-api-us.security.gallagher.cloud`         | `44.193.42.111`, `3.209.194.103` |
| Global Cloud Services API Gateway      | `services.security.gallagher.cloud`                     | `15.197.141.103`, `76.223.78.39` |


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