How to build a router



Recently my curiosity made me explore another crazy idea: to use a full PC as a router, and connecting to internet with a plain modem.

A full PC should allow a better (and powerful) option if used as router, but I have no experience about installing a firewall (something that is already embedded in a router) nor how to configure it, so I’m here to ask for help again :bigsmile:

There are two area to be explored: hardware and software. Let’s start with the hardware.

If I understood correctly, the hardware to be used is something like the following scheme:

Internet --> modem --> Router-PC --> Switch --> one or more regular PC

If I’m not wrong, it is not needed a huge CPU power to build a router: a regular modem/router certainly doesn’t have a quadcore CPU.

So my first question: is an Atom 510 CPU sufficient? I can find a board for a not too high price, and it has a low power consumption (very important for a machine that should run 24/7). It certainly will consume more than a regular modem/router, but I’m curious about this and asking for suggestion certainly will not enlarge the ozone hole :bigsmile:

Second question. I think that two NICs are needed: one to connect the router-PC to the modem, and another to connect the router PC to the switch. Is that correct or not? If not, what is the correct scheme?

Because of in the Router PC it must be installed only the operative system (a linux distro dedicated to this maybe?) and the firewall, maybe is possible to install everything on an USB pendrive. This will reduce power consumption and an USB pendrive certainly costs lesser than a SSD. Is that possible or an USB pendrive will be unreliable in time so is better to use a regular HDD? USB pendrives are certainly slower than a regular HDD, so I wonder if this will cause a bottleneck that will make totally useless to have a full PC as router because a regular modem/router will be a lot faster. Any hints about that?

About RAM: is 1 GB enough or not? If I’m not wrong, most routers use only 64 MB of RAM, so with 1 GB the machine should be able to manage a huge amount of connections (useful for P2P for example, but also if many PCs are connected at the same time to the same modem).

About the PSU. I found a nice mini-ITX case with an included 70W PSU, so this should be not an issue.

Did I forget something in the hardware list?

Let’s talk about software now. What Linux distro should I use? The only one that I found is Endian, but it seems not really simple to use :eek:

Another advantage of a full PC is that it should have enough resources to run an excellent QoS, much more efficient than a regular modem/router. Is that correct?

Any suggestion is welcome :bow:

Thanks :slight_smile:


Yeah there’s a lot to learn if your new to Linux, there should be decent guides out there if do some searching ie. “how to build a hardware firewall”.

The D510 cpu should be plenty fast and 1-2GB ram should be fine. You can probably use a laptop HDD, they use very little power. I’m not sure about the adapters available for compact flash drives but that could be an option too.

Holy cow Sergio you just hit 25,000 posts! :smiley:

  1. You certainly don’t need a powerful for a home connection. An old Pentium 133 will go a long way and an Atom CPU will work just as food as long as you don’t want to run a lot of things at the same time.

  2. Yes, you’ll need one more NIC. Highly recommended an Intel one instead of cheapish Realtek.

  3. Have a look at or (m0n0wall is a smaller dist that is more limited than pfsense). You can on the other hand install a full dist like FreeBSD (both above are based on it) if you want to use it for something more than just routing / firewall. Getting 1Gb of RAM will be more than enough for routing but if you want to use it as NAS or run multiple sevices at least 2Gb (per stick) is recommended. Most ITX cases uses 2.5" drives (laptop HDDs).

  4. A PC will have more processing power (in most cases) but it will also draw more power.


Oh and btw,
Be a bit careful with the ION boards as they may / may not work as good as the ones with Intel chipsets.


Thanks for you answers:)

You know… curiosity is an incurable “disease” :stuck_out_tongue: :bigsmile:

My idea was to use the machine exclusively as router/firewall, but I realized that I have to choose a board with a PCIe slot, because installing a gigabit NIC is useless on a PCI slot :doh:

I’ll take a look at these distro :slight_smile:


You can use the builtin NIC which usually is Gbit although Realtek inwards and use a PCI 100Mbit or 1000Mbit as WAN. Getting a dedicated computer for this is on the other hand just a waste unless you have 100/10 or better connection.



I had a look at endian distro… it is intimidating regarding how much options can be set :eek:

Building a firewall is anything but easy :doh:


pfsense is most likely better but oh well…


Currently the Linksys router firewall is the simplest I found. There are only two options: enabled and disabled :bigsmile:

btw, I’m taking a look also at pfsense and monowall :slight_smile: