I have found Ethernet hubs to be invaluable over the years. One way that I use them is to help separate 2 networks that share a common ISP. For example I have a cable modem internet connection and I want to have a corporate network and a guest network so I do MODEM --> HUB --> guest and corporate router on separate wires then I manually assign static IPs from the ISP for both routers. I like the hub because it maintains no tables and blindly repeats everything. I have been having a very hard time finding hubs lately (new ones any way). Does anyone know any good resources to find hubs? Don't say ebay... I don't like purchasing used gear. I have seen some new ones but they are ridiculously priced. Over $100... WOW. If I can not find them I may have to go with the old standby of 3 routers where you have a top level router that feeds into 2 smaller routers but i do not want to do that. I have had really good success with the hubs in the past for this. My goal is simple I want 2 networks with independent IP address to be able to share one link from the ISP but be completely incapable of communicating with each other directly so the guest router feeding through the corporate router is out because then the corporate router would be addressable from the guest router. It may sound confusing and a bit backwoods but it has always worked for me very well with low cost and overhead. I am open to other idea and methodologies. I have considered VLANS but they have not made it into the price bracket of my customers yet. Usually very small business SOHO size but wanting a little bit more than SOHO can provide. My concern is absolute security. The 2 networks (or at least the assets on that network) can never be able to directly address the other in any way.
Network setup 2 separate networks share 1 ISP link
Good to hear from you. I did a search on www.newegg.com for ethernet hubs and found some, like you said from $20 to over $200. Like all things, when the supply is short the cost is high.
Even though, I understand your desire for 2 separate IP networks. Your solution on using hubs is not a good one for the sake of what you want "absolute security." By using a hub, any one single port still gets the any electrical signal sent from any one port. This will be true regardless if you put all of your devices on different IP networks because of the basic functionality of the hub.
You've got a few options though like you've mentioned. The only way to guarantee that your two networks will never be able to directly connect to each other directly is to put them on completely separate equipment. Or you can use two hubs, each directly connected to your router on separate router interfaces.
I would recommend the usage of a switch with vlans. The cost is a little more but as you're seeing the cost of hubs are not a lot less anymore. With the switch, you can create your 2 separate vlans and use a single router port (100 Mbps or higher) along with access control lists on your router to keep the traffic separated.