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Connect your servers with a private network

A private network between your Rack4 servers in one location, for databases, backups and moves. Nobody else can reach it, and it is free.

updated · 3 min read

Turn on the private network on each server that should be on it: open the server in the panel, go to Network, then Private network, and choose join the private network. Each server gets a second network card with an address like 10.240.0.10, and your servers can then reach each other on those addresses.

What it is

  • Only your servers. Each account's servers in a location share a network of their own. Other customers' servers and the internet can't reach it, and the host itself takes no part in it.
  • Same location. Servers in the same location can join; the panel lists your other servers on it.
  • Free, and not counted. Traffic on it doesn't count towards your monthly transfer.
  • No restart. The card is plugged into the running server. A server that's off gets it when it next starts.

Good uses: a website talking to its database on another server, backups from one server to another, and moving to a bigger server.

Turn it on

In the panel: the server, then Network, then Private network, then join the private network. It's plugged in within a minute. The page then shows the server's private address and network card, and the lines to set it up.

From the command line:

bash
rack4 private on web-1
rack4 private status web-1

Or with the API: PUT /servers/:id/private-network with {"enabled": true}.

Set the address up on the server

The card arrives without an address; you add it once. Open the serial console first, so a mistake can't lock you out of SSH. The panel shows these lines with your server's own address and card filled in.

Ubuntu and most Debian images (netplan: ls /etc/netplan shows a file). Save this as /etc/netplan/60-rack4-private.yaml, with your address and, for <mac>, the network card's MAC from the panel, keeping the indentation exactly as shown:

yaml
network:
  version: 2
  ethernets:
    private:
      match:
        macaddress: "<mac>"
      addresses:
        - 10.240.0.10/16

Then:

bash
sudo chmod 600 /etc/netplan/60-rack4-private.yaml
sudo netplan try

netplan try puts the network back if you don't confirm within two minutes, but it leaves the file in place: if something went wrong, delete the file before you try again.

AlmaLinux, Rocky and Fedora (NetworkManager: nmcli general answers). With your address, and the card's MAC for <mac>:

bash
IF="$(ip -o link | awk -F': ' '/<mac>/ {print $2}')"
sudo nmcli con add type ethernet con-name rack4-private ifname "$IF" ipv4.method manual ipv4.addresses 10.240.0.10/16 ipv6.method disabled
sudo nmcli con up rack4-private

Check it works

On the server, ip -br addr lists the private address. Then ping another of your servers on its private address:

bash
ping -c 3 10.240.0.11

If it doesn't answer, check that the other server has joined and has its address set up too.

Security

  • Only your own servers can reach a private address. Nothing is routed off the private network: it has no gateway, so it can't reach the internet either.
  • The panel firewall covers your server's public address, not the private one. To limit which of your servers can reach a service, use a firewall on the server itself.
  • A server can only send from its own private address and card; it can't pretend to be another.

Turn it off

Choose leave the private network on the same page, or run rack4 private off web-1. The card is unplugged; anything using the private address stops working. Delete the netplan file (or sudo nmcli con delete rack4-private) afterwards.

A server restored from the recycle bin comes back without its private network: join again if you need it.

Ready when you are

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