I’ve always been a fan of running a router/firewall on bare metal. Don’t like the idea that bouncing my hypervisor for maintenance or a kernel upgrade takes down my whole network.

virtualising means you can make more use of resources on system rather than having two systems and dedicating one to specific task.

On the other hand you can bork the hypervisor and then be without internet and possible become the families public enemy #1 :)

But it’s generally pretty stable. Not use opnSense but do have a virtualised router using SophosXG. One nic from the VM is tied to vmbr0 which is the main virtual bridge that ties my virtual machines to the rest of the network. The IP is my default gateway.

the second NIC is done as PCIe pass through and this connects direct to my cable modem.

I could have bound this NIC to another vmbr and would have worked just as well. However there was some discussion in r/proxmox about performance impacts if you have a very fast internet connection (something to with srv-io iirc).

So, I run OPNsense in a VM on Proxmox. There is only one drawback I am aware of, which is when I update the Proxmox host itself, I’ll need to attach a monitor/keyboard/mouse to it. Theoretically, if the upgrade was fully automatic and never needing any intervention or user input, it’d be possible without: But the reality is more that it might need user input, but the OPNsense VM will not be booted i.e. network will be down i.e. I need direct access to the Proxmox host.

Separate device for opnsense is better. It’s more secure and you can have proper physical network segmentation. You would want to do that if your budget allows. This also allows you to have a stable network while you’re playing with proxmox. Having a solid network core is important. Everything expands and build on top of that.

You can still achieve network segmentation on proxmox but you have to careful and have enough phisical NICs. You can mess things up easily if you start using proxmox firewall. You still need to do updates on both opnsense and proxmox so reboots will be needed. I would say opnsense needs more reboots than proxmox.

As for backups snapshotting is nice to have. Opnsense allows you to backup configuration. You can setup daily backups to Git repo. As long as you restore to the same hardware (same number and order of NICs) you will be ok. Restoring to different device requires changes in config. Config is XML file.

I don’t recommend it on the basis of being absolutely obnoxious to configure and maintain. If anything goes wrong with the internet in my household, someone will wake me up at 4am to removed about it too. I tried proxmox and xcp-ng and with both I would run into cases where I couldn’t get into the management interface for any vm or the VM host. Connected directly, monitor would be blank and keyboard did nothing. Force reset, couldn’t find any reason and eventually it would happen again. Now I have a separate device with a probably overkill CPU and 5x the hard drive space needed due to smaller drives being more expensive at the time, but no network or vm access problems.

I run pfSense on a 2 node Proxmox “cluster” (cluster in quotes because I don’t have quorum for automatic failover). Each host has a dedicated NIC for the firewall’s WAN port attached to my modem which is in bridge mode. When I need to do maintenance on the node hosting the FW I do a live migration to the other node. I drop one ping during the migration.

Honestly, when I was designing it I didn’t think it would work…but here we are…lol.