XenServer 6.2 – Hetzner host – Additional Subnet Configuration


I have a dedicated server on Hetzner, on which I have installed XenServer 6.2 .

The server comes with one public IP address. I purchased an additional subnet containing 6 usable IP addresses, for use with the guest VMs. So, I have a total of 7 IP addresses.

I used the Hetzner guide (http://wiki.hetzner.de/index.php/Citrix_XenServer/en) to complete the installation.

In the guide, in the "Network Configuration" section, there are two things for which I need clarification.

  1. There are instructions to "Configure the Host as a Router". What exactly is the purpose of this? What does it achieve? What does it allow me to do?

  2. In the instructions to "Configure an additional subnet", the first usable IP of the subnet I have purchased is assigned to the host. The host already has an IP address assigned (which came along with the server). In addition, the first IP of the subnet is also assigned. Why does the host need 2 IP addresses? Out of 7 IP addresses, I end up with just 5 IPs for my guest VMs.


Best Answer

  1. Hetzner's firewalls are blocking virtual mac addresses, that's why you gotta do it the "routing way". This means that the IP-subnet you've ordered has been set to be routed via your server's IP. As you use XenServer, your VM's can use the IP-addresses pointed to you.

  2. You need to give your server an IP address from your new subnet allowing it to communicate there. You need to create an alias for your bridged interface and set one of the usable IP to it. This way the VM's can communicate to the outer world and use that IP as a gateway. Getting a 7-IP address subnet equals 5 usable IP's. The first and last are unusable (network/broadcast).

One thing what I hate about Hetzners subnet, is that they charge monthly for additional ip's (subnet).

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