Making a NetworkManager profile with a fixed address, switching it to DHCP while keeping a DNS server, and seeing where Ubuntu stores it. The lab works on a spare interface, never on the one you're connected over. The chapter's Wi-Fi task needs Wi-Fi hardware and isn't part of the lab.

Before you start

The lab adds a spare wired interface lab0 (a dummy interface that comes back at every boot). If NetworkManager isn't installed, as on Ubuntu Server, the lab installs it; it leaves the interfaces it already finds alone, and reset removes it again. Don't activate the profile.

Tasks

Create a profile office for interface lab0 with the fixed address 10.10.10.50/24, gateway 10.10.10.1 and DNS 10.10.10.1, without activating it.
Make the profile use DHCP for its address but keep the DNS server 10.10.10.1. Task 1 stays passed once you've done this.

When le-lab check passes, remove the profile as the chapter shows, or leave that to le-lab reset.

Hints

nmcli connection add type ethernet ifname lab0 con-name office ipv4.method manual ipv4.addresses ... ipv4.gateway ... ipv4.dns ... connection.autoconnect no. nmcli -g ipv4.method,ipv4.addresses connection show office prints manual and 10.10.10.50/24, and sudo ls /etc/netplan/ shows a new 90-NM- file.
nmcli connection modify office ipv4.method auto, clearing the old address with ipv4.addresses "" ipv4.gateway "", and ipv4.ignore-auto-dns yes so DHCP's DNS servers aren't used.
nmcli connection delete office.