title: 1:1 NAT created at: Sun Nov 10 2024 08:32:02 GMT+0000 (Coordinated Universal Time) updated at: Sat Feb 08 2025 14:22:50 GMT+0000 (Coordinated Universal Time) --- # 1:1 NAT # Overview !! Warning: !! We **strongly** recommend that you **only** perform these actions on a new installation of cPanel & WHM. **Do not** attempt a 1:1 NAT configuration on an existing production server. When you install cPanel & WHM, the installer will detect whether your server resides on a NAT-configured network. If the installer detects a NAT-configured network, your server will configure itself for NAT mode and attempt to automatically map local IP addresses to public IP addresses. !! Important: !! If you use a NAT environment, your server **must** reside in a 1:1 NAT configuration to install cPanel & WHM. !! For cPanel & WHM services to function correctly, you or your network administrator **must** enable [loopback (or hairpin) NAT](https://en.wikipedia.org/wiki/Network_address_translation#NAT_loopback) on both the server and its firewall. Loopback NAT allows the server to access a public IP address internally from its corresponding private IP address. !! For a list of ports that you must open to allow cPanel & WHM services to function on your server, read our [How to Configure Your Firewall for cPanel & WHM Services](https://docs.cpanel.net/knowledge-base/general-systems-administration/how-to-configure-your-firewall-for-cpanel-services) documentation. # The mapping process The system attempts to map all non-loopback IP addresses bound to any network interface on the server to a public IP address.  To complete this process, the system performs the following actions: 1. Your server will send an outgoing connection from each local IP address to the `http://myip.cpanel.net/v1.0/` server. 2. The `http://myip.cpanel.net/v1.0/` server responds with the public IP address from which it received the request. 3. The system maps the local IP address to this public IP address. !! Warning: !! We do **not** recommend that you map more than one local IP map address to a single public IP address. # Manage IP addresses You can manage the maps for local and remote IP addresses with the following WHM interfaces: * The [*Add a New IP Address*](https://docs.cpanel.net/whm/ip-functions/add-a-new-ip-address/) interface (*WHM » Home » IP Functions » Add a New IP Address*). * The [*Show or Delete Current IP Addresses*](https://docs.cpanel.net/whm/ip-functions/show-or-delete-current-ip-addresses/) interface (*WHM » Home » IP Functions » Show or Delete Current IP Addresses*). * The [*IP Migration Wizard*](https://docs.cpanel.net/whm/ip-functions/ip-migration-wizard/) interface (*WHM » Home » IP Functions » IP Migration Wizard*). Each interface displays the warning notice *NAT mode enabled* if NAT is enabled on your server. !! Warning: !! If multiple local IP addresses match the same public IP address, the system will **only** map the first local IP address in the `/var/cpanel/cpnat` file. # The build\_cpnat script The `/usr/local/cpanel/scripts/build_cpnat` script uses the `http://myip.cpanel.net/v1.0/` server to map local IP addresses to public IP addresses. However, if you wish to use a different IP address lookup service, perform the following steps: 1. Open the `/etc/cpsources.conf` file with a text editor and add the following line: ```javascript MYIP=https://ifconfig.me/ip ``` 1. Run the `/usr/local/cpanel/scripts/build_cpnat` script !! Note: !! For more information about the `build_cpnat` script, run the following command: !! `/usr/local/cpanel/scripts/build_cpnat --man ` !! If you accidentally delete your `cpnat` file or the file becomes becomes corrupted, rebuild it with the `/usr/local/cpanel/scripts/build_cpnat` script. !! The `/var/cpanel/cpnat` file acts as a flag file for NAT mode. If the installer mistakenly detects a NAT-configured network, delete the`/var/cpanel/cpnat` file to disable NAT mode. 1. Update your cPanel accounts’ local IP addresses in WHM’s [*IP Migration Wizard*](https://docs.cpanel.net/whm/ip-functions/ip-migration-wizard/) interface (*WHM » Home » IP Functions » IP Migration Wizard*).