Where does Proxmox get the gateway IP?

[pxmxadm]

Hi,

pardon my lack of networking understanding. I have vmbr0 assigned an IP, say, 10.10.10.10/24 with gateway 10.10.10.1. I then want to tag vlans on on bridge. So I try to create vmbr0.1080 with an IP 10.10.11.11/24 in vlan 1080 but if I specify vlan 1080 gateway IP in the web UI, it throws error:

Parameter verification failed. (400)

gateway: Default gateway already exists on interface 'vmbr0'

If I don't specify the gateway and commit the changes anyway, somehow I am able to ping it. Where does it get the gateway info from? Thanks.

 

[bbgeek17]

Hi @pxmxadm ,

There is no gateway configured for your VLANs. You have Layer 2 (L2) connectivity, allowing hosts on the same subnet to broadcast and receive ARP messages from other hosts within the subnet.

To examine your routing table for more details, you can do:
ip r

Any traffic that the host cannot reach directly will be sent to the gateway of your primary network. This means the source IP will be the original one, not the VLAN IP.

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Blockbridge : Ultra low latency all-NVME shared storage for Proxmox - https://www.blockbridge.com/proxmox

 

[pxmxadm]

Thanks, @bbgeek17. I'd like to do what I have in the current VMware environment - vmk0 = ESXi management, vmk1 = NFS storage backend, vmk2 = vMotion and each is on its own VLAN. I only have 2 x 10Gb ports and want to maintain network redundancy. Is it possible to achieve the same in Proxmox? Thanks.

 

[_gabriel]

I am able to ping it

ping who ?
ping local subnet ip doesn't require a gateway. gateway is required only to go out local subnet ip.

 

[gurubert]

if I specify vlan 1080 gateway IP in the web UI, it throws error:

A host can only have one default gateway. If you add a second interface with its own IP subnet just do not add a default gateway in its configuration.

 

[bbgeek17]

I'd like to do what I have in the current VMware environment - vmk0 = ESXi management, vmk1 = NFS storage backend, vmk2 = vMotion and each is on its own VLAN. I only have 2 x 10Gb ports and want to maintain network redundancy. Is it possible to achieve the same in Proxmox?

Yes, you can certainly place multiple VLANs on the same physical interface, or multiple interfaces.
There will be one default gateway per system, likely on the management network. You can add static routes to particular VLANs if you need to access hosts outside of storage or "vmotion" VLANs via that particular VLAN, otherwise they will be non-routable.

As this is more of a basic Linux Networking than PVE specific question, you can find many guides about VLAN configuration.
For example: https://www.youtube.com/watch?v=Qx40bgKAKe0

Cheers

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Blockbridge : Ultra low latency all-NVME shared storage for Proxmox - https://www.blockbridge.com/proxmox