You should consider opnsense instead of pfsense in any case.

If installing Wireguard as your VPN is a possibility, Install Opnsense + Wireguard on old hardware and forget about AES.

Any VPN that terminates on the firewall (be it site to site or remote access / "road warrior") may be affected, but not all will. Some VPN tech uses very efficient computations. Notably affected VPNs are OpenVPN and IPSec / StrongSwan.

If the VPN doesn't terminate on the firewall, you're in the clear. So even if your work provided an OpenVPN client to you that's affected by AES-NI, because the tunnel runs between your work laptop and the work server, the firewall is not part of the encryption pipeline.

Another affected technology may be some (reverse) proxies and web servers. This would be software running on the firewall like haproxy, nginx, squid. See https://serverfault.com/a/729735 for one example. In this variation of the check, you'd be running one of these bits of software on the firewall itself and either exposing an internal service (such as Nextcloud) to the internet, or in the case of squid doing some HTTP/S filtering for a tightly locked down network. However, if you just port forwarded 443/TCP to your nextcloud server (as an example), your nextcloud server would be the one caring about the AES-NI decrypt/encrypt. Like VPN, it matters to the extent of where the AES decrypt/encrypt occurred.

Personally, I'd recommend you get AES-NI if you can. It makes running a personal VPN easier down the road if you think you might want to go that route. But if you know for sure you won't need any of the tech I mentioned (including https web proxy on the firewall), you won't miss it if it's not there.

Edit: I don't know what processors you're looking at that are missing AES-NI, but I think you have to go to some really really old tech on x86 to be missing it. Those (especially if they're AMD FX / Opteron from the Bulldozer/Piledriver era) may have other performance concerns. Specifically for those old AMD processors (Not Ryzen/Epyc), just hard pass if you need something that runs slightly fast. They're just too inefficient.

Encryption and Decryption can be resource intensive processes. Most firewalls typically have a lower throughout for VPN connections than they do for just straight routing because of the extra processing power required for VPN. Based on what little I've read, it seems like CPU's with AES-NI are capable of handling the encryption process more efficiently which probably reduces system load and allows for more throughput.

This only helps in situations where your firewall is either serving or connecting to a VPN. It won't make any difference if your connecting to a work VPN form your computer. Even if you are hosting a VPN connection from your firewall, AES-NI is probably overkill unless you're planning to connect a bunch of clients to it at the same time or plan to do something like file transfers at Gigabit speeds.

It's for encryption and decryption so only valid for VPN tunnels initiated by pfsense. Not a needed feature by any means if you don't selfhost stuff and want to setup VPN tunnels and run a lot of traffic through (like say media through Jellyfin)

Pfsense has an openvpn server and client built in. Also if you are using site-to-site ipsec vpns it can be useful. I think it will also use the extensions if you run a web proxy to inspect tls traffic. If you just use it for a nat gateway, then you don't need aes-ni or even most of the features Pfsense provides.

I'm not sure what you're shopping for with AES-NI but I can strongly recommend the HP T730 and T740 thin clients if you're trying to build a budget home firewall machine. Both support AES-NI (but obviously not Xeon QAT) and the t730 is cheap on eBay. Drop whatever NIC and an SSD in and you're off to the races with OPNSense. The T740 is performant enough to run OPNSense on Proxmox if that's your thing, you'll have plenty of spare processing time to do something else on the machine beyond routing/firewalling a 1-2Gb home connection.

If you don't use a VPN on the router, you won't need it.

But what if you decide to set one up so you can VPN in while on the road? Personally, I'd rather have it and not need it, than need it and not have it...as well as "buy once, cry once" rather than need to upgrade down the line.

Acronyms, initialisms, abbreviations, contractions, and other phrases which expand to something larger, that I've seen in this thread:

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