First off; I'm not a networking expert so forgive me if anything I ask here is blindingly obvious, or I use the terminology incorrectly :)

My company has recently moved office to a new building where internet access is included in the rent. However, from what I can gather all machines in the building simply connect to one big switch (I can see lots of unknown machines on the network, and presumably they can also see our machines).

For the record, we have about six Windows 7 machines, a Windows Server 2008 machine and some printers.

I'd like to create an isolated network for the company but still maintain access to the internet. How can I achieve this?

We have a couple of off-the-shelf routers that were used in our previous office - will we need to buy additional hardware to create the setup we want (a managed switch and/or firewall, for example?)

1 Answer 1


There is several different approaches you could take. The best solution depends on your needs. In my answers I assume that your office has wall-mounted ethernet sockets, that currently connect directly to the central switch(es).

  • You can use one of your off-the-shelf routers and configure it to provide a different subnet on it's LAN interfaces, connect it's WAN interface to one of the ethernet sockets in the office, and run your own cabling to the PCs in your office (or alternatively have them connect wirelessly).
  • If you have access to the networking equipment in the building, you can buy a new switch and router, and have it set up alongside the other equipment. Then it's a simple matter of moving the patch cables in the switching rack from the old switch to your new one. Usually a switching rack will have a few patch panels where you can connect a patch cable from a switch to one of said patch sockets, that will then connect to one of the ethernet sockets in the office. These are usually labelled both on the wall socket and on the patch panel.
  • You could have whoever currently administers the networking equipment create a separate VLAN for your office on the existing switch, and configure the existing router to serve a new subnet only to that VLAN.

For the most control over your networking environment, I'd say get your own switch and router in the rack and have the ISP assign you a new public IP for your office only. But then, it really depends on your needs.

  • Thanks Mark, that sounds like pretty much what I expected (we do have wall-mounted sockets that go to a network cabinet controlled by the building). Ideally I'd like to go for option 1 - this seems like the simplest - but I can't seem to get the WAN port on my router to act as an internet connection when plugged into the wall socket...
    – DAVco
    Jul 30, 2015 at 18:01
  • This particular connection setup is called "double NAT". It's not normally a problem, but maybe the existing network is set up in a non standard way. If you are able to "just connect" a PC by plugging it into the wall, make sure your router is set to get an IP address by DHCP from the WAN port. Then set up your router to act as a DHCP server on the LAN side. When you can connect a PC to your own router and get an IP address on your own LAN, try pinging the routers IP address. If that works, try pinging the IP of the router on building net. Finally try pinging an IP address on the internet.
    – Mark Qvist
    Jul 31, 2015 at 6:28

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