We just had a new internet connection (WiMAX type of thing) installed in one of our remote offices. The customer premises presentation is just an ethernet cable and basically the whole internet is looking in on that wire so I need to set up a firewall.

The configuration is such that there is a subnet with two usable IP addresses (/30). One of the usable IP's is the gateway address and the other is a single free IP address to attach a PC or other device.

We've got a few PC's at this location and need to get them all sharing this connection.

We already have a Billion BIPAC 7402NX wireless router on site (this was configured to use a 3G dongle). I'm wondering if I can configure the Billion as a traditional ethernet router/firewall and have the office network on a RFC1918 private range and have it route traffic to the WiMAX network?

If this isn't possible, what devices would you recommend to achieve this?

PC1  ---------    
PC2  --------+-- (int. LAN on 192.168.1.x) ---->  [Router/FW]  ---> WiMAX  
PC3  ---------  

I'm looking for a device that will allow me to do NAT as I would understand it if this were a traditional ADSL connection (i.e. single public IP on the WAN side, multiple private IP's on the internal network) to our internal LAN.

I'd prefer a device built for purpose and don't have spare equipment or time to knock up a Linux based Router/Firewall....but if overwhelmingly convinced I can change my mind.

3 Answers 3


It looks like your Billion BIPAC 7402NX device only has DSL and USB Internet connections and your new connection is ethernet. You can buy a cheap Linksys BEFSR41 which gives you a ethernet WAN port and 4 LAN ports. You would need to turn off the DHCP server on the Billion device and use the DHCP server on the Linksys. If you want a more robust device for your firewall that allows you to create more complex rules or setup a VPN, I would recommend a Sonicwall such as a TZ 100 series.

  • Ah ha...this looks like the kind of thing I'm after. I'm guessing many cable-co's present on ethernet hence the requirement for this kind of device?
    – Kev
    Feb 15, 2010 at 15:39
  • +1, didn't know about that Linksys one.
    – Massimo
    Feb 15, 2010 at 15:40
  • Just about to order one of these LinkSys boxes from ebay. Thanks for the recommendation. Oddly enough I accidentally bought one of these (or a v. similar mode) a few years back mistaking it for a bargain ADSL router. Thanks for the answer.
    – Kev
    Feb 15, 2010 at 17:57
  • Yes, many cable companies just give you an ethernet connection with one IP. Some phone companies would give you a DSL modem that provided 1 IP over ethernet as well but it has become much more common for them to provide modems that are a basic firewall and wireless access point now.
    – Matthew
    Feb 15, 2010 at 21:55
  • The BEFSR41 did the trick. Cheers.
    – Kev
    Feb 20, 2010 at 1:09

If your Internet connections comes via an Ethernet cable, you need an Ethernet-to-Ethernet router (which can also do NAT).
Sounds simple, but it actually isn't, because consumer-grade equipment usually doesn't need to do that, so it's quite difficult to find such a device on the market: routers usually have ADSL, ISDN, cable and so on as their WAN interface.
This can of course easily be done by enterprise-grade products, such as Cisco routers, but this can get expensive.

I strongly suggest a PC with two network cards and software routing, be it Linux IPTABLES, Windows RRAS or whatever else you like.

  • +1 Smoothwall would work well in this scenario.
    – Lazlow
    Feb 15, 2010 at 17:56

as there is a lot of such devices produced, just look in google about some kind of "wimax router soho". but be informed, that if your LAN will be accessible from outside of the world(internet) depends from your Mobile ISP SLA/Private or Public IP/port forwarding availability etc./ Hope it helps.

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