Making OPNsense Unreachable after Changing LAN IPv4 DHCP on Hetzner

Making OPNsense Unreachable by Changing LAN IPv4 DHCP on Hetzner

In this article, we will cover the process of changing the LAN IPv4 DHCP on an OPNsense server hosted on Hetzner. This can be useful when you want to make the OPNsense server unreachable from the client server, and instead, use OPNsense for network access to the public network.

Prerequisites

• An OPNsense server hosted on Hetzner
• A client server that is currently connected to the OPNsense LAN

Changing the LAN IPv4 DHCP on OPNsense

To change the LAN IPv4 DHCP on OPNsense, follow these steps:

1. Log in to the OPNsense web interface.
2. Navigate to Services > DHCPv4.
3. Click on the Edit button next to the LAN interface.
4. Under the General Configuration section, change the Subnet to a new, unique IP address range that is not currently in use on your network.
5. Under the DHCP Server section, change the Range to match the new IP address range you specified in step 4.
6. Click the Save button to apply the changes.

Making OPNsense Unreachable from the Client Server

Now that you have changed the LAN IPv4 DHCP on OPNsense, the client server will no longer be able to reach OPNsense using the old IP address. To make OPNsense completely unreachable from the client server, you will need to disconnect the client server from the OPNsense LAN and connect it to a different network.

Using OPNsense for Network Access to the Public Network

Once the client server is connected to a different network, you can use OPNsense to provide network access to the public network. To do this, follow these steps:

1. Log in to the OPNsense web interface.
2. Navigate to Firewall > NAT.
3. Click on the Add button to create a new NAT rule.
4. Under the Interface dropdown, select the WAN interface.
5. Under the Protocol dropdown, select TCP and UDP.
6. Under the Destination field, enter the IP address of the public network.
7. Under the Redirect Target IP field, enter the IP address of the client server.
8. Click the Save button to apply the changes.

• Changing the LAN IPv4 DHCP on OPNsense will make the OPNsense server unreachable from the client server.
• To use OPNsense for network access to the public network, you will need to disconnect the client server from the OPNsense LAN and connect it to a different network.
• You can then use OPNsense to provide network access to the public network by creating a NAT rule that redirects traffic from the WAN interface to the IP address of the client server.

References

• OPNsense DHCPv4 Configuration
• OPNsense NAT Configuration