Does anyone know of a low power server/pc that have 2 NIC's, so it can be used for a (OpenBSD) firewall?
Sandra
What sort of load do you need to handle and (if you plan on needing to NAT) how many states do you anticipate needing to track? If under 50Mbit and 20k states or so, I'd highly recommend using an ALIX embedded computer. I have many of these deployed as router/firewall/vpn devices, running PFSense. PFSense is based on FreeBSD, so it's likely getting OpenBSD running on it will be quite easy. All of the units like this I've deployed are using the ALIX 2d3 board, which has three network interfaces (can add as many VLAN interfaces as you want to any of these physical interfaces), a 500MHz processor, and 256 MB RAM. They're rock-solid stable, run very cool, and draw a max of 6 watts or so.
If you need something with a bit more horsepower, then follow Wesley's advice. HP rackmount servers are very good, as long as, like he said, you stay away from the very low-end servers which are really just desktop motherboards stuffed into a rackmount case.
Edit: Total cost for the ALIX 2d3 solution will be about $150 for the board, power supply, case, and CF card.
Really, you just need to pick out one of the lower-end servers offered by a major vender. Just determine if you need a desktop or rackmount form factor. For example, HP's ML/DL 100 series of tower/rackmount servers would be good. Just avoid the lowest of the low such as the ML 110/115. Lowest end servers usually have some important corners that have been cut like disk controllers, NICS and management features.
You could get a decent lower end server for under $1,000 easy.
How about something based on a mini-itx motherboard?
I am suprised that nobody mentioned the fit-PC2i that always seems to come up in this application area.
I 2nd the Alix + Pfsense.
I built one (http://tothelasttribe.com/blog/2009/04/building-a-firewall-pfsense-on-an-alix-2d3/), and have nothing but positive things to say about it.
-Josh
Living outside of the US, the cost for one of those embedded systems no longer becomes an advantage once shipping is factored into.
For me, I run m0n0wall on an Atom 330 instead (http://perpetuallybored.com/2010/02/12/high-performance-and-affordable-router-with-m0n0wall-and-atom/). Not the most low powered solution, but it works.
As you've explicitly asked for a low power machine I suggest that any old PC will suffice. At work I'm using a PC that was replaced because it was too low spec for use as a workstation, with a pair of extra NICs thrown in (one for the DMZ). At home I'm using an old Celeron that was going to be thrown out by someone I know, also with an extra pair of NICs installed.