Configuring VLAN with Multiple Proxmox Instances on a Single Switch

[Hanes]

Hello everyone,

I'm relatively new to Proxmox but a big fan of the product. Today, I'm facing a challenge for which I need assistance.

I have two Proxmox instances connected to the same physical unmanaged switch. I want to create a VLAN with a mix of VMs from both hypervisors, similar to how I would create a Linux bridge on a single Proxmox instance and assign it to any VM or LXC.

I believe this issue could potentially be resolved using an OVS bridge and other related configurations.

Can you please assist me in finding a solution to this problem?

 

[jlauro]

You didn't really describe what problem you are having.

Are you sure the unmanaged switches will work with VLANs. It's hit or miss at best if switches will forward that, and even those that do it's not really any better than not doing a VLAN at all and just running multiple nets on the same network. (Well, maybe the proxmox can limit tcpdump a little, but on the wire it will make no difference).

It's worth getting some used managed switches from ebay, or Zyxel has some low cost switches that can support tagging.

 

[Hanes]

You didn't really describe what problem you are having.

Are you sure the unmanaged switches will work with VLANs. It's hit or miss at best if switches will forward that, and even those that do it's not really any better than not doing a VLAN at all and just running multiple nets on the same network. (Well, maybe the proxmox can limit tcpdump a little, but on the wire it will make no difference).

It's worth getting some used managed switches from ebay, or Zyxel has some low cost switches that can support tagging.

Thank you for your input and suggestions.

To provide a clearer example of the problem, let's consider a scenario with two hypervisors and three VMs. These VMs are configured to form a MongoDB replica set, and I want them to be part of the same VLAN/subnet with IP addresses like 10.0.0.10, 10.0.0.11, and 10.0.0.12. The challenge is to achieve this within a VLAN.

While I understand the potential limitations of unmanaged switches, my belief is that using Open vSwitch (OVS) might offer a solution. By creating an OVS bridge between the VM instances distributed across multiple hypervisors, I hope to establish the desired network configuration without relying on managed or Layer 3 switches that support tagging or VLAN.

I welcome any further insights or recommendations on this approach, and if there are hardware-related constraints, I'm keen to understand those as well.

 

[jlauro]

I haven't used OVS with proxmox, so I can't help too much... That said, from what I understand OVS uses VXLAN (maybe it's an option and not a requirement(?)), and VXLAN requires jumbo frames for standard packets. You will want to verify your unmanaged switch support jumbo frames, or you will likely need one that does. Technically you could probably force the guests to 1450 (or 1446 if also pretending tagging) instead of the standard 1500...

BTW, VXLAN doesn't support fragmentation. It requires jumbo frames, or in theory lower than standard ethernet MTU should work.