Configure a Static IP Address and DNS for Internet Access on Zyxel FLEX H Series Firewall

This article explains how to configure a Zyxel USG FLEX H Series firewall to connect to the Internet when the ISP does not require authentication and has provided a public static IP address, subnet mask, gateway, and DNS server address.

The configuration includes setting the static IP address on the WAN interface and configuring the DNS server on the firewall.

If the ISP requires a specific MAC address to provide Internet access, the WAN interface can also be configured to use a custom MAC address.

1. Configure the WAN Interface with a Static IP Address

Note: If your Internet Service Provider requires a PPPoE connection, refer to the following article for instructions: How to Configure PPPoE on the WAN Interface of Zyxel USG FLEX H Series.

Go to Network > Interface > Interface and open the WAN interface configuration.

Under Address Assignment, select Use Fixed IP Address.

Enter the information provided by your Internet Service Provider:

• IP/Network Mask — enter the public static IP address and network mask.
• Gateway IP — enter the IP address of the default gateway.

Make sure that Enable Interface is enabled.

Click Apply to save the settings.

Default SNAT

Expand Advanced Settings and make sure that Default SNAT is enabled.

Default SNAT allows devices on the LAN to use the WAN interface to access the Internet.

Connectivity Check

The Connectivity Check feature monitors the availability of the Internet connection through the WAN interface.

The firewall periodically sends a test request to a specified destination, such as 8.8.8.8. If the destination cannot be reached, the firewall can detect that the WAN connection may be unavailable.

This feature is optional and is mainly useful for monitoring the WAN connection and WAN failover scenarios.

To enable it, turn on Enable and configure the following settings:

• Method — select the method used to check the connection. For example, ICMP.
• Period — specify how often the firewall performs the connectivity check.
• Timeout — specify how long the firewall waits for a response.
• Attempt — specify the number of attempts before the check is considered unsuccessful.
• Source — specify the source IP address if required.
• Destination — enter the IP address or host used to check the connection. For example, 8.8.8.8.
• Success Criteria — select the condition used to determine whether the connectivity check is successful.

For a basic Internet connectivity check, you can use ICMP with 8.8.8.8 as the destination.

2. Configure the DNS Server

DNS translates domain names, such as google.com, into IP addresses. A DNS server is required for the firewall and connected clients to resolve domain names and access Internet services by name.

Go to System > DNS & DDNS > DNS.

Under Global Zone Forwarder, a default DNS server is configured automatically. You can keep the default settings or add a specific DNS server for Internet connections.

Click Add and configure the following settings:

• Domain — enter * to apply the DNS server to all domain zones.
• Type — select User-defined.
• DNS Server — enter the DNS server address provided by your ISP. You can also use a public DNS server, such as 8.8.8.8, if your ISP does not require a specific DNS server.
• Query Via — select the WAN interface used for the Internet connection.

A user-defined DNS server allows you to specify which DNS server the firewall uses for queries sent through the selected WAN interface.

Note: If your network uses internal DNS servers or internal domain names, make sure that the selected DNS configuration can resolve those names. Do not replace a required internal or ISP-provided DNS server with a public DNS server unless appropriate for your network.

Click Apply to save the settings.

3. Configure a Custom MAC Address

Some ISPs use MAC address binding and allow Internet access only from a specific MAC address. In this case, you can configure the USG FLEX H Series to use a custom MAC address on the WAN interface.

Go to Network > Interface > Interface and open the WAN interface configuration.

Under MAC Address, select Overwrite Default MAC Address.

Enter the MAC address provided by your ISP or the MAC address of the device previously connected to the ISP network.

Make sure that the MAC address is entered in a valid format, for example:

XX:XX:XX:XX:XX:XX

Click Apply to save the settings.

Note: Only change the default MAC address if your ISP requires a specific MAC address. Otherwise, keep Use Default MAC Address selected.

4. Verify the Internet Connection

After configuring the WAN interface and DNS, verify that the Internet connection is working correctly.

Connect a computer to a LAN port of the USG FLEX H Series firewall. The computer should automatically receive an IP address from the firewall's DHCP server.

Open a command prompt on the computer and perform the following tests:

1. Test the Internet connection by IP address:

   ping 8.8.8.8

2. Test DNS name resolution:

   ping google.com

If both tests are successful, the WAN connection and DNS resolution are working correctly.