Ubuntu 18.04 guests which cloned by virtualbox have the same ip but different mac address in NAT network

I tried to build a group of Virtual machine in Virtualbox, and connect them with NAT network. The main information shows as below:

The Virtualbox version: 6.0.12
The Ubuntu guest version: ubuntu-18.04.2
The NAT network info: NetworkName: natnet22 IP: 192.168.13.1 Network: 192.168.13.0/24 IPv6 Enabled: No IPv6 Prefix: fd17:625c:f037:2::/64 DHCP Enabled: Yes Enabled: Yes loopback mappings (ipv4) 127.0.0.1=2

When I finish creating an Ubuntu machine, the DHCP server maybe assign ip 192.168.13.4 for it. But when I cloned the machine and I change the mac address of the cloned one. The DHCP server still assign ip 192.168.13.4 for the cloned one.

Why the cloned Ubuntu one get the same ip with source? I need them have different ip in the NAT network to control them. Please help me solve the problem.

3 Answers

In newer Ubuntu versions, netplan is used for configuring the network. The file /etc/machine-id is used to create the DHCP identifier by default, rather than using the MAC address of the NIC.

When a Ubuntu system is cloned, the cloning process may change the MAC address of the NIC but it typically doesn't automatically change /etc/machine-id.

On your two systems, you can compare the contents of /etc/machine-id and they're probably the same.

You have two options:

1. Change the machine-id on at least one of the servers (huangjunpo's answer)

   user@host:~$ cat /etc/machine-id
   d8dcd93cd8bffce0f7ed73875eb5be3a
   user@host:~$ sudo rm /etc/machine-id
   user@host:~$ sudo systemd-machine-id-setup
   Initializing machine ID from random generator.
   user@host:~$ cat /etc/machine-id
   4b603489b08541ce9127791047081f46

2. If using netplan, change the way netplan constructs the client identifer for DHCP to use the MAC address by adding dhcp-identifier: mac to your netplan config file in /etc/netplan. Add it under any interface you need to, and be careful of indentation in the yaml file. (see netplan.io - examples)

   user@host:~$ cat /etc/netplan/00-installer-config.yaml
   # This is the network config written by 'subiquity'
   network: ethernets: enp3s0: dhcp4: true dhcp-identifier: mac version: 2

After making this edit, you will have to apply it to make it have effect.

sudo netplan apply

Note that /var/lib/dbus/machine-id is linked to /etc/machine-id.

user@host:~$ ls -l /var/lib/dbus/machine-id
lrwxrwxrwx 1 root root 15 May 8 20:30 /var/lib/dbus/machine-id -> /etc/machine-id

Try the following commands on cloned vm:

sudo ip address flush scope global
sudo dhclient -v

Run below commands in bash shell. Use machine's id as identifier.

sudo rm /etc/machine-id
sudo systemd-machine-id-setup