I'm in a bit of a unique situation in that I have lots of extra hardware that I need to sell or use. I don't mind using some of it to build a "WAY overbuilt" routing PC. I don't mind the extra power draw as long as it's not ridiculous and ... I like building PCs.
So, my question is, are there any gotchas I need to look out for when trying to build a PC (likely ITX) to be a router? I know I probably need an external NIC - already have one on the way.
In general, anything I need or need to avoid? e.g. are AM4 AMD chips ok? I have a spare AMD Ryzen 3 3300x which again, I know would be way overkill but I don't mind using it. Other AMD options are a 3000G or 3200G (with integrated graphics) but wondering if I care/want that. I guess it might be nice to hook up a monitor and I probably don't wanna waste a video card (that said, I have some old GT 710s or something).
I also have a Celeron G5920 I could use. Thoughts on Intel vs. AMD?
Is RAM speed important for performance? i.e. should I use two sticks (thus dual-channel) 3200/3600 or will I be okay with the oldest/worst DDR4 sticks I have (2666)? There is no question if I'm going Celeron obv. (max support is 2666).
I have gigabit down 100mb up and want to build something that will get me full gigabit (wired) with QoS. I already have APs so I'm not concerned about WiFi, but I may throw a PCIe card in the PC for good measure, we'll see.
intel often has lower idle power consumption over desktop amd (exception maybe some thin client soldered amd CPUs)
older intel (4th to 11gen gen) tend to have less power consumption vs newer intel
mind space needs for your additional nic card
a wisely selected PSU does a lot for lower power consumption
1 RAM instead of >1: less power consumption, speed does not really matter
get a silent cpu fan
get a nic card that does not need a fan
consider using it as LAN SAMBA file server as well
have a bios that has auto-power-on-on-AC-power-connect (most have it, but some have issues)
there are unfamiliar things, when you have not used x86 OpenWRT before:
by default, only 1 port for LAN is active, another 1 for WAN. The technical IDs decide about the default oder. The remaining ports by default are disabled and need to be manually enabled in OpenWRT config.
instead of an OpenWRT reset button you use an attached keyboard
you can administrate it via attached keyboard and monitor and see the boot log on screen
...and at least compare the prices (130-250 EUR) of alderlake-n/ n100 based mini-PCs with four 2.5GBASE-T ethernet ports, which will only need 5-10 watts idle. Those quickly pay for themselves on your electricity bill.
I'd use one of those, as then you have a direct console without any additional hardware.
Speed of disk and RAM is no consequence for routing tasks. If you go wild and run enterprise IDS/IPS (intrusion detect/prevent systems), like Snort or Suricata, then maybe fast RAM becomes beneficial, but packet processing otherwise is an extremely low load workflow. Even big DNS- and IP-based blocklist processing is plenty fast on little 6-800 MHz ARM processors, so you need not worry about it.
If I can get it to <30W which should be doable with a celeron or 3000g and no GPU and a good PSU (I have a platinum SF750)... then power cost should be pretty negligible. ~12.5cents/KWh for me so like an extra $25ish per year.
It might be waste of expensive components (e.g. PSU), at least initially, but then I'm set up to do more with it in future if I decide to as well.
I think I'll actually do it open air on a test bench rig I have that I don't have another use for right now, so at least I'll save on that instead of buying a fancy SFF PC case.
edit: just looked at the efficiency curve of an SF750. That would be a waste. Will use the best PSU option I have on hand since I'm gonna do a test bench anyway so I can go mATX and full size cheap PSU if I want. Cool.
You can buy a fanless 8 core intel i5-305 box with 6x 2.5 GbE for around $350 :
Or go for the 4 core intel N100 - I got mine for 255€, with 8 GB RAM and 256 GB
NVMe.
You can add a wifi card inside (and connect antenna outside), put two big ssd and as much ram (ddr5)...
It will do firewall, switching, NAS, home-assistant.. everything you want while eating MUCH less power (≈10W) than mismatched luxury parts you would put together, have no moving parts, ...