[SOLVED] Why setting up networkd to a static IP does not work?

Issue

After deploying a virtual appliance inside VirtualBox, the guest has a DHCP IP address and everything works fine. The problem is that I need to have this VM on a static IP address.

This VM is the latest Bitnami Postgres, running on Debian 11.

When performing ifconfig, I get this for the relevant network interface :

enp0s3: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 192.168.2.196  netmask 255.255.255.0  broadcast 192.168.2.255
        inet6 fe80::a00:27ff:fe5e:6c9  prefixlen 64  scopeid 0x20<link>
        ether 08:00:27:5e:06:c9  txqueuelen 1000  (Ethernet)
        RX packets 1431  bytes 113648 (110.9 KiB)
        RX errors 0  dropped 244  overruns 0  frame 0
        TX packets 306  bytes 22928 (22.3 KiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0
        device interrupt 19  base 0xd000  

I have tried following the vendor's recommended steps to assign a static IP address, namely by adding the file /etc/systemd/network/25-wired.network, however this does not work :

[Match]
Name=enp0s3

[Network]
Address=192.168.2.52
Gateway=192.168.1.1

As indicated by the DHCP result, the subnet is 255.255.255.0 (or 192.168.2.52/24) so I changed the config file to :

[Match]
Name=enp0s3

[Network]
Address=192.168.2.52/24
Gateway=192.168.1.1

But then it complains that the Gateway is not on the same subnet! Changing it to :

[Match]
Name=enp0s3

[Network]
Address=192.168.2.52/16
Gateway=192.168.1.1

yields no error when restarting the network service, however routing is broken and nothing is accessible; the guest can't ping any machine, and no machine can ping the guest!

I tried adding various sections, like Route], [Address], etc. I am at a loss.

Solution

You define your subnet to be at 192.168.2.0/24, witch excludes the possibility to include your gateway at 192.168.1.1 !

The correction done by the system is correct: Indeed, the mask for that IP/Gateway configuration is 16, or netmask>24.

You should review your desired network configuration, and remember that the netmask 24 will define a minimum subnet address of x.y.z.1 -> x.y.z.254 . In both cases x.y.z remain the same.

Your gateway needs to be inside of the subnet. If you really want to use the IP 192.168.2.196 with the gateway at 192.168.1.1, try the netmask 23. That being said: I doubt that your gateway uses the netmask 23 (seems a standard router configuration to me).

Answered By - ricard0

Answer Checked By - Gilberto Lyons (WPSolving Admin)