I am currently setting up a Proxmox box that has the usual selfhosted stuff (Nextcloud, Jellyfin, etc) and I want all of these services in different containers/VMs. I am planning to start sharing this with family/friends who are not tech savvy, so I want excellent security.

I was thinking of restricting certain services to certain VLANs, and only plugging those VLANs into the CT/VMs that need them.

Currently, each CT/VM has a network interface (for example eth0) which gives them internet access (for updates and whatnot) and an interface that I use for SSH and management (for example eth1). These interfaces are both on different VLANs and I must use Wireguard to get onto the management network.

I am thinking of adding another interface just for “consumption” which my users would get onto via a separate Wireguard server, and they would use this to actually use the services.

I could also add another network just to connect to an internal NFS server to share files between CT/VMs, and this would have its own VLAN and require an additional interface per host that connects to it.

I have lots of other ideas for networks which would require additional interfaces per CT/VM that uses them.

From my experience, using a “VLAN-Aware” bridge and assigning VLANs per interface via the GUI is best practice. However, Proxmox does not support multiple VLANs per interface using this method.

I have an IPv6-only network, so I could theoretically assign multiple IPs per interface. Then I would use Linux VLANs from within the guest OS. However, this is a huge pain and I do not want to do this. And it is less secure because a compromised VM/CT could change its VLAN tag itself.

I am asking if adding many virtual interfaces per CT/VM is good practice, or if there is a better way to separate internal networks. Or maybe I should rethink the whole thing and not use one network per use-case.

I am especially curious about performance impacts of multiple interfaces.

  • Trainguyrom@reddthat.comEnglish
    2·
    6 months ago

    It really sounds like you need to dive into firewall rules. Generally you lean on your firewall to allow and restrict access to services. Probably the easiest place to start is to setup pfsense/opnsense since it has a really clean interface for setting up rules. Proxmox’s built in firewall is nice too, but configuring the firewall per VM would probably get annoying and difficult after a while

    And as you learn more about firewalls learning how subnetting works will allow for more efficient rules (for example, if you have 192.168.0.0/23 192.168.2.0/24 and 192.168.3.0/ 24 for your networks that you’re allowing traffic to/from you can just enter one firewall rule for 192.168.0.0/22 rather than 3 separate rules)

    • anon2963@infosec.pubOPEnglish
      1·
      6 months ago

      Thank you, that is a very good point, I never thought of that. Just to confirm, best standard practice is for every connection, even as simple as a Nextcloud server accessing an NFS server, to go through the firewall?

      Then I could just have one interface per host but use Proxmox host ID as the VLAN so they are all unique. Then, I would make a trunk on the guest OPNsense VM. In that way it is a router on a stick.

      I was a bit hesitant to do firewall rules based off of IP addresses, as a compromised host could change its IP address. However, if each host is on its own VLAN, then I could add a firewall rule to only allow through the 1 “legitimate” IP per VLAN. The rules per subnet would still work though.

      I feel like I may have to allow a couple CT/VMs to communicate without going through the firewall simply for performance reasons. Has that ever been a concern for you? None of the routing or switching would be hardware accelerated.