Can I use an Opengear device as a gateway router?

Yes, while your Opengear device may not be suitable to replace a dedicated router appliance, it has a reasonably comprehensive set of firewall router features and can be used as a temporary gateway (e.g. during new site turn ups) or as a permanent gateway for smaller LANs (e.g. retail or kiosk applications).

This mode is particularly effective when utilizing its built-in cellular modem as a WAN connection.  Also consider the Failover To Cellular (F2C) feature, which allows the Opengear device to offload its cellular IP to a dedicated router appliance.

As an example, find below basic steps to configure an Opengear device as a cellular gateway router (the DHCP server steps are optional, if you'd prefer to use static settings on the internal network).

Cellular gateway router instructions

Click System -> Firewall -> Forwarding & Masquerading

• Next to Network Interface, check Dialout/Cellular
• Scroll down to Enable IP Masquerading (SNAT) and check Dialout/Cellular
• Click Apply

Click System -> IP -> Network Interface

• Set Configuration Method to Static
• Set an IP Address of 192.168.0.1
• Set a Subnet Mask of 255.255.255.0
• Ensure Gateway is blank (the Opengear device will be the gateway for this network)
• Click Apply

Click System -> DHCP Server

• Check the DHCP Server enable checkbox
  
• Check Use interface address as gateway
• Check Use this interface address as the DNS server 
• Click Apply

Scroll down to Dynamic Address Allocation Pools

• Click Add
• Enter an DHCP Pool Start Address of 192.168.0.100
• Enter an DHCP Pool End Address of 192.168.0.120
• Click Apply

Click System -> Services

• Check the Enable DNS Server/Relay enable checkbox
• Click the Service Access tab
• In the Network Interface column check the DNS Server/Relay enable checkbox

Click System -> Dial -> Internal Cellular Modem

• Select Enable Dial-out
• Enter settings from your carrier, e.g. APN
• Click Override returned DNS servers
• Set DNS Server 1 to 8.8.8.8
• Scroll down and click Apply

Attach a network host running a DHCP client (e.g. a laptop set to obtain network settings automatically) to the Opengear's primary Ethernet (NET1).  The network host will be automatically configured to use the Opengear device as its gateway router.