My setup looks like this:

WiFi router plugged into cable router

In the interest of security, I'd like to separate the wired network (where the Workstation is plugged in) from the wireless subnet. I don't trust some of the devices in the wireless subnet - they are vulnerable to malware and risky because torrenting warez.

I'm not interested in the network itself, just Internet access for all. So I'd like the wireless devices to only talk to the Internet, not to each other and certainly not to the Workstation.

How can I accomplish this?

  • 1
    I don't think most cable modems are full featured enough to do what you're asking. You may want to look at adding a router. This would not be a bad idea regardless of how you end up architecting your network. Everything behind your router would be yours and physically changing ISPs would not alter your "back of house." You could do it with a Layer-3 switch (which is what a router is) but buying a router would be a cheaper solution. Could look at setting up a UTM with a spare PC also; like untangled or endian
    – M15K
    Dec 18, 2013 at 17:05
  • Well I have a router... 2 routers, one wired and one wireless. The internet coming to my house is UTP cable, I don't use a modem.
    – John
    Dec 18, 2013 at 17:13

2 Answers 2


I hesitated a bit to offer up Rodney's answer as I'm not sure that many consumer based ISP gateways have this level of granularity in the setup. Also a firmware change, hardware change, ISP change basically renders your network inoperable until you reconfigure that new ISP device (if it even has the same options).

Rodney is talking about basically trying to slice the pie, lets say your "cable router" has the lan site network configured like The device itself has an address of It has a DHCP server daemon that will hand out IPs in the range of So that is your wired interface.

You can then setup your "wireless router" with an address of, just like a static host on your network. It will use the "cable router" IP as it's gateway. Then you can setup your wireless firewall to block traffic from Depending on how the Network Processors are architect-ed, it could possibly bog down your wireless router and devices if it has to process a bunch of rules. Anyway it would hand out a small subnet of addresses maybe the private side is like is the gateway and you are handing out

It could all be moot and possibly your "cable router" will let you setup VLANs (virtual lans, with virtual gateways) May be called Zones or some other name that infers network segregation. All in all I would get a SMB sized Router from Ebay.


Put your wired network on a different subnet (and VLAN if your router/switch supports it).

On either router (cable or wireless) add a firewall rule to block traffic between your wireless subnet and your wired subnet.

  • Could you please exemplify or give a little more details, I'm not sure how to do these things.
    – John
    Dec 18, 2013 at 17:46

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