Windows – Create WiFi hotspot without internet from laptop

The purpose of home/consumer routing equipment (I use the term loosely to refer to access points, hubs, switches, routers, modems, and any combination of the above) is to:

• Remove the complexity associated with manually setting up a full-featured, robust and secure network (dedicated equipment, especially for the home, is almost as easy as plug and play)

• Provide reliable configurations designed to work with a wide variety of client devices (or, you know, provide unreliable configurations that only work with that vendor's client devices.... AHEM Linksys I'm looking at you)

• Tightly control the security of the network by providing a hardware firewall on a locked down device where the firewall cannot easily be altered, bypassed or disabled by programs (in other words, if you ONLY ran a firewall on your client computer, it would be riskier than having one on the router, which is a more secure environment due to how restrictive it is)

• Provide better signal reception for wifi, more uptime, and power savings: the routing hardware itself consumes very little energy from the wall socket, especially when compared to the power consumption of a desktop or laptop. Also, the routing hardware provides better signal strength than you can expect from a laptop or desktop, because the shape of the router and the location of the antennae plays a large role in signal strength and reliability. And since the routing hardware uses integrated components that are low-power, active cooling such as fans, which add noise and consume power, are not necessary.

By trying to use computers as a passthrough for your internet connection and sharing that connection with downstream client devices, you lose all of the above benefits:

• You lose the low-complexity factor because configuring a reliable routed network on a computer (regardless of operating system) is worlds more complicated than plugging in a router

• You lose the reliability because rebooting your computer for updates, crashes, etc. is natural, and each time you reboot, any downstream clients lose the connection. Also, you can have programs on your computer taking up all the resources (CPU time, RAM, etc) that can slow your network to a crawl.

• You lose the tight control of the IP-layer security because clever programs can disable your firewall on your computer (especially on an OS such as Windows) but it is much less likely to be possible to compromise a router, especially one running the most up-to-date firmware

• You lose the excellent signal reception of wifi routers, which are tuned to provide longer range broadcasts than most "USB dongles" and PCI-E/Mini-PCIE cards that fit in laptops and desktops

• You lose the power savings, because if anybody wants to use your network from one of the downstream clients, you have to keep the routing PC(s) online and running. If you're routing it through desktops in particular, the power consumption for older-generation video cards and CPUs, even while idle, can be pretty ridiculous.

For these reasons, I think you are asking how to set up a configuration that is just plain inadvisable.

On the other hand, it is possible to manually design your own highly reliable, low-power router using a miniature computer (such as a PandaBoard or a plug PC, a mini ITX, etc). Generally you would run a stable, mature, secure operating system such as OpenBSD or Linux on the device, and you would not use the computer for normal desktop usage, such as playing games, surfing the web, and so on. The device would be "dedicated" to the task of routing. If configured properly, such a device can provide all the benefits of a consumer router, plus adds configurability so that a networking expert can fine-tune the parameters of the routing, such as using a custom Active Queue Management packet scheduling algorithm.

If that's the way you want to go, I think you should educate yourself more about networking technologies and the details of how to configure a reliable routing package on a *NIX box (that is, Linux, BSD, etc). Then you can look into buying a small, low-power device, or build your own and shop for the best-quality network cards, etc. If you make the right decisions along the way, you could be very happy with the result, and it wouldn't be very expensive to do (the operating system software is free, if you use BSD or Linux).

Anyway, that's getting pretty off-topic. The short answer is that I think the best thing for you to do is to not try this. Unless you're up for configuring/building your own dedicated router, the best way to go would be:

<<internet>> --> <<any number of wireless access points, routers, or switches, as you deem appropriate>> --> <<client computers, both desktops and laptops, both wired and wireless>>

Unless you really know what you're doing (and if you did, honestly, you probably wouldn't be asking this particular question on SU), you don't want a computer "in the middle". Especially not a Windows computer that is also in service as an entertainment/productivity desktop computer.

Get a WiFi extender or a client bridge device (something that can connect to WiFi and allows connections via an ethernet port), and connect it to your phone's hotspot.

Then, disable the access point (repeating/extending function) on the WiFi extender and plug an ethernet cable from a LAN port on the extender to the WAN port of a router.

You can usually find old routers on Craigslist for about $15 to $25. Connect all your devices to the access point broadcasted from the router, and that should do. The router, is given one IP, and then splits it up for other devices.

WiFi extenders do not have routing functionality. The reason for this, is because it would be more expensive to build it that way, and... Traditionally it would cause less issues because it connects to one LAN network pool. Aka, the devices on the main access point can still initiate connections with devices connected to the repeater.