Network doesn't work

[OstharzRC]

Hey,
i have just installed Proxmox for the first time on a KVM Server and created an Ubuntu Server 24.04 VM. The VM doesn't have a Network connection and i don't know why? Does someone have an idea?
Do I have to pay special attention to something when configuring Proxmox on a server that is not in the local network?

 

[mariol]

Do you have DHCP-Server on your network? If not, Ubuntu will not be able to obtain an IP address. In this case, you will need to enter the IP/gateway/DNS manually.

Please also post your network configuration for the Proxmox VE node and your VM configuration:

cat /etc/network/interfaces

qm config <vmid>

Please also "pveversion -v".

 

[OstharzRC]

Do you have DHCP-Server on your network? If not, Ubuntu will not be able to obtain an IP address. In this case, you will need to enter the IP/gateway/DNS manually.

Please also post your network configuration for the Proxmox VE node and your VM configuration:

cat /etc/network/interfaces

qm config <vmid>

Please also "pveversion -v".

I can't tell you if there is a dhcp server because this would probably be setup by the hosting provider if there is one, right? Here are the outputs of the commands (i did all of them on the node, is it right like this?)

 

[mariol]

Thanks for the output. Config looks good. As I see you have a public /24 IP range from your provider.
DHCP can run in there. But that's rather unusual. With hosting, you usually have to take care of this yourself. Try configuring an IP manually in your VM -> does it work then?

For example:

IP 80.75.218.197/24
Gateway 80.75.218.1
DNS 8.8.8.8

 

[OstharzRC]

Thanks for the output. Config looks good. As I see you have a public /24 IP range from your provider.
DHCP can run in there. But that's rather unusual. With hosting, you usually have to take care of this yourself. Try configuring an IP manually in your VM -> does it work then?

For example:

IP 80.75.218.197/24
Gateway 80.75.218.1
DNS 8.8.8.8

Where exactly do i have to configure that?

 

[meyergru]

I would sincerely question that the OP has a /24 range. The whole range is the (only) AS of a prepaid hoster. I would bet that there is only one IP allocated to this system. Normally, you would need (at least) two IPs, one for the Proxmox host and one for your VM. And usually, both would be assigned statically, one in the Proxmox configuration (as shown) and one in the VM.

But since you probably do not have two IPv4, you will have to resort to a setup with masquerading and port 22 and 8006 used by Proxmox. Be advised, that is not for the faint of heart and guessing from the questions you ask, this will be quite difficult to do. I did this twice and had to resort to a remote console to get out of the pit whenever I messed up.

This works only for one VM (or at least combo of port and VM), if you only have one IP. For multiple VMs, it is best to use a VM router like pfSense or Proxmox to create a reverse proxy, which can use DNS names to differentiate between internal VMs / services.

The alternative is to pay for additional IPs, but given your hoster only has 256 of them, that might be infeasible.

P.S.: For hosted setups, a /24 netmask is often wrong, since other hosted machines are on the same network, but separated. Normally, you would use a point-to-point setup. If you don't, you cannot reach your "neighbors" on the same subnet, because no gateway will be used.

 

[OstharzRC]

I would sincerely question that the OP has a /24 range. The whole range is the (only) AS of a prepaid hoster. I would bet that there is only one IP allocated to this system. Normally, you would need (at least) two IPs, one for the Proxmox host and one for your VM. And usually, both would be assigned statically, one in the Proxmox configuration (as shown) and one in the VM.

But since you probably do not have two IPv4, you will have to resort to a setup with masquerading and port 22 and 8006 used by Proxmox. Be advised, that is not for the faint of heart and guessing from the questions you ask, this will be quite difficult to do. I did this twice and had to resort to a remote console to get out of the pit whenever I messed up.

This works only for one VM (or at least combo of port and VM), if you only have one IP. For multiple VMs, it is best to use a VM router like pfSense or Proxmox to create a reverse proxy, which can use DNS names to differentiate between internal VMs / services.

The alternative is to pay for additional IPs, but given your hoster only has 256 of them, that might be infeasible.

P.S.: For hosted setups, a /24 netmask is often wrong, since other hosted machines are on the same network, but separated. Normally, you would use a point-to-point setup. If you don't, you cannot reach your "neighbors" on the same subnet, because no gateway will be used.

Thanks for the explenation. So are you saying that with a reverse Proxy this would work and not be too difficult to set up? If yes i would be really happy if you could explain how to do this.

 

[meyergru]

Alas, that works quite well but is even more complicated than just getting one VM to work besides Proxmox itself.

I explained that here, but be warned:

1. It is really hard stuff involving learning another tool of the trade - OpnSense - and then, a reverse proxy like HAproxy or Caddy on top of it, including ACME certificates.
2. I cannot coach you through it. Essentially, you will have to learn it by yourself or pay someone to do it.

 

[OstharzRC]

Alas, that works quite well but is even more complicated than just getting one VM to work besides Proxmox itself.

I explained that here, but be warned:

1. It is really hard stuff involving learning another tool of the trade - OpnSense - and then, a reverse proxy like HAproxy or Caddy on top of it, including ACME certificates.
2. I cannot coach you through it. Essentially, you will have to learn it by yourself or pay someone to do it.

Ok, then i probably won't do this... If i get a dedicated Server (for example from Hetzner) this won't be a problem, right?

 

[meyergru]

Technically, there is little difference, so I maintain that this is not easy.

Matter-of-fact, I use Hetzner, too.

You usually get one IPv4 from Hetzner as well (per default, there is none these days). You can order multiple additional IPs or whole ranges (if you can argue that you need them) at an additional cost. Hetzer has instructions on using Proxmox in multiple scenarios:

https://community.hetzner.com/tutorials/install-and-configure-proxmox_ve/de

While there are videos and other ressources on how to do this, it is everything but easy. Last time I looked, you even had to use a remote console for Proxmox installation or use a complex trick in order to be able to provisioning it initially.

https://www.youtube.com/watch?v=N0-4Nq52trw
https://www.youtube.com/watch?v=6K8enRH1Woo
https://www.youtube.com/watch?v=ncWQCGFok-I

The best solution is a Proxmox installation with only one IPv4, using one OpnSense VM that opens access to a virtual LAN where all the other VMs reside on. Then, you use port forwards or a reverse proxy to access them. Ports 22 and 8006 are used for Proxmox itself, whereas all other ports are forwarded to the OpnSense WAN.

In addition to that, you can also get a separate /56 IPv6 range that can be provisioned to the client VMs via OpnSense for a one-time fee.

 

[OstharzRC]

Technically, there is little difference, so I maintain that this is not easy.

Matter-of-fact, I use Hetzner, too.

You usually get one IPv4 from Hetzner as well (per default, there is none these days). You can order multiple additional IPs or whole ranges (if you can argue that you need them) at an additional cost. Hetzer has instructions on using Proxmox in multiple scenarios:

https://community.hetzner.com/tutorials/install-and-configure-proxmox_ve/de

While there are videos and other ressources on how to do this, it is everything but easy. Last time I looked, you even had to use a remote console for Proxmox installation or use a complex trick in order to be able to provisioning it initially.

https://www.youtube.com/watch?v=N0-4Nq52trw
https://www.youtube.com/watch?v=6K8enRH1Woo
https://www.youtube.com/watch?v=ncWQCGFok-I

The best solution is a Proxmox installation with only one IPv4, using one OpnSense VM that opens access to a virtual LAN where all the other VMs reside on. Then, you use port forwards or a reverse proxy to access them. Ports 22 and 8006 are used for Proxmox itself, whereas all other ports are forwarded to the OpnSense WAN.

In addition to that, you can also get a separate /56 IPv6 range that can be provisioned to the client VMs via OpnSense for a one-time fee.

Ok... so i always have to do some trickery or have to buy additional IPv4 Adresses, correct? With more IPv4 Adresses i won't have such a complicated setup? Is there a tutorial for the virtual Lan method?

 

[OstharzRC]

Technically, there is little difference, so I maintain that this is not easy.

Matter-of-fact, I use Hetzner, too.

You usually get one IPv4 from Hetzner as well (per default, there is none these days). You can order multiple additional IPs or whole ranges (if you can argue that you need them) at an additional cost. Hetzer has instructions on using Proxmox in multiple scenarios:

https://community.hetzner.com/tutorials/install-and-configure-proxmox_ve/de

While there are videos and other ressources on how to do this, it is everything but easy. Last time I looked, you even had to use a remote console for Proxmox installation or use a complex trick in order to be able to provisioning it initially.

https://www.youtube.com/watch?v=N0-4Nq52trw
https://www.youtube.com/watch?v=6K8enRH1Woo
https://www.youtube.com/watch?v=ncWQCGFok-I

The best solution is a Proxmox installation with only one IPv4, using one OpnSense VM that opens access to a virtual LAN where all the other VMs reside on. Then, you use port forwards or a reverse proxy to access them. Ports 22 and 8006 are used for Proxmox itself, whereas all other ports are forwarded to the OpnSense WAN.

In addition to that, you can also get a separate /56 IPv6 range that can be provisioned to the client VMs via OpnSense for a one-time fee.

and also... why would i buy a subnet from hetzner if a single IP is cheaper per ip?

 

[meyergru]

Yes, as I said, even the first IP consts extra.

And why would you order a range? Because single IPs are not from consecutive ranges and are thus harder to configure. Anyway, if you only want name-based services, you can get away with at most 1-2 IPv4. I am not quite sure if a range drops the need for dedicated MACs as well.

Hetzner limits the IPs to a specific MAC, which further complicates things, because your VM will have to use the correct MAC to work.

 

[OstharzRC]

Technically, there is little difference, so I maintain that this is not easy.

Matter-of-fact, I use Hetzner, too.

You usually get one IPv4 from Hetzner as well (per default, there is none these days). You can order multiple additional IPs or whole ranges (if you can argue that you need them) at an additional cost. Hetzer has instructions on using Proxmox in multiple scenarios:

https://community.hetzner.com/tutorials/install-and-configure-proxmox_ve/de

While there are videos and other ressources on how to do this, it is everything but easy. Last time I looked, you even had to use a remote console for Proxmox installation or use a complex trick in order to be able to provisioning it initially.

https://www.youtube.com/watch?v=N0-4Nq52trw
https://www.youtube.com/watch?v=6K8enRH1Woo
https://www.youtube.com/watch?v=ncWQCGFok-I

The best solution is a Proxmox installation with only one IPv4, using one OpnSense VM that opens access to a virtual LAN where all the other VMs reside on. Then, you use port forwards or a reverse proxy to access them. Ports 22 and 8006 are used for Proxmox itself, whereas all other ports are forwarded to the OpnSense WAN.

In addition to that, you can also get a separate /56 IPv6 range that can be provisioned to the client VMs via OpnSense for a one-time fee.

so i always have to do some trickery or have to buy additional IPv4 Adresses, correct? With more IPv4 Adresses i won't have such a complicated setup? Is there a tutorial for the virtual Lan method?

 

[meyergru]

You need a means to separate your VMs carrying services on port 80/443, so you either need different routeable IPs which the DNS names map to, or a reverse proxy that does this via DNS name mapping.

The reverse proxy can run on an OpnSense VM. To have a firewall in place in front of your service is a bonus in and of itself, so I suggest to get OpnSense in either case. However, that means you need to learn and configure OpnSense in the first place and some Proxmox trickery to get it working.

As I said, even the Promox initial setup may not be as straightforward as you think.

Whether you need or want the reverse proxy setup is basically your choice, but it is very flexible and allows to cnetralise certificate provisioning as well - yet it is admittedly complex. I pointed to the respective Caddy and HAproxy tutorials on OpnSense already. While you could do this via separate IPs and routing as well, it costs you per IP and month and essentially is no less complex.

I also pointed to the tutorial for Proxmox in a datacenter in a previous post and videos as well. The case with one virtual IP can be extended to multiple ones.

 

[OstharzRC]

You need a means to separate your VMs carrying services on port 80/443, so you either need different routeable IPs which the DNS names map to, or a reverse proxy that does this via DNS name mapping.

The reverse proxy can run on an OpnSense VM. To have a firewall in place in front of your service is a bonus in and of itself, so I suggest to get OpnSense in either case. However, that means you need to learn and configure OpnSense in the first place and some Proxmox trickery to get it working.

As I said, even the Promox initial setup may not be as straightforward as you think.

Whether you need or want the reverse proxy setup is basically your choice, but it is very flexible and allows to cnetralise certificate provisioning as well - yet it is admittedly complex. I pointed to the respective Caddy and HAproxy tutorials on OpnSense already. While you could do this via separate IPs and routing as well, it costs you per IP and month and essentially is no less complex.

I also pointed to the tutorial for Proxmox in a datacenter in a previous post and videos as well. The case with one virtual IP can be extended to multiple ones.

I did the open sense install via this tutorial(https://www.youtube.com/watch?v=CFNvwB6fFag&ab_channel=Netcube) but the ping shown at https://youtu.be/CFNvwB6fFag?si=gvs8ONYzh3H6INEA&t=882 doesn't work. The only difference to the tutorial was that in https://youtu.be/CFNvwB6fFag?si=cQT6BS5L2wJeQaHh&t=201 my network device just had one line. It said "iface ens18 inet manual" so i just changed it to match the tutorial (with my Ip of course). Was this wrong? Is the IPv6 shown at that moment coming form the provider or can i set it however i want?

 

[meyergru]

At 882 seconds in the video, he does a ping to 8.8.8.8, which is not an IPv6, but the public IPv4 of Google DNS, so it is assumed to show that outgoing IPv4 works. If it does not, you have done something wrong. As I said, especially the variant with only one IP is really hard to get right - there is no "only difference". You will have to follow those instructions to the letter with the only obvious exception of specific IPvs being different for you.

That being said, AFAIK that specific guide does not even handle IPv6 at all and I have not verified if it works for IPv4. It also does not cover VPN or reverse proxies. BTW: I have forgotten to mention the topic of Wireguard VPN, which you will need to securely connect to the virtual LAN that you create on the remote OpnSense.

The sheer number of steps to get that right is almost a guarantee that you get something wrong in the process (been there, done that). Diagnosing upcoming problems (and they will) takes a lot of expertise and as I said, I cannot teach you that. With all due respect, the questions you ask show that you are a beginner at networking, who has picked one of the hardest tasks to master in that field.

As already noted, if I were you, I would do one of two things, depending on what you want to achieve:

1. If you need this setup for doing any kind of business and for fast results, hire someone to do it. It might take you weeks, if not months to to it yourself at this point.
2. If you want to learn and have time, start out with a setup you can phyiscally control at your home. With a datacenter setup, any problem you have will effectively disconnect you from the machines, so you need a remote console to fix it. You can get that free for a few hours from Hetzner, but not days on end.

Lots to learn here: Proxmox, OpnSense, IPv4, IPv6, reverse proxies, routing, masquerading, Wireguard, VPN, certificates.