How to set up a network bridge for VM on KVM Ubuntu 18 laptop

UI thought I had successfully configured KVM on my Ubuntu 18 Lenovo Thinkpad Carbon i5 (3rd gen?), when I realized none of the VMs had any internet connection.

I followed these linked directions to set it up: https://linuxconfig.org/install-and-set-up-kvm-on-ubuntu-18-04-bionic-beaver-linux

I ran

sudo apt install qemu-kvm libvirt-clients libvirt-daemon-system bridge-utils virt-manager 

with no problem, but I found their instructions on editing /etc/network/interfaces confusing.

The directions suggest using the ip a command to find out what “network interface” you have. My output looks like this:

1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000     link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00     inet 127.0.0.1/8 scope host lo        valid_lft forever preferred_lft forever     inet6 ::1/128 scope host         valid_lft forever preferred_lft forever 2: enp0s25: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc fq_codel master br0 state DOWN group default qlen 1000     link/ether 54:ee:75:92:1a:60 brd ff:ff:ff:ff:ff:ff 3: wwp0s20u4: <BROADCAST,MULTICAST,NOARP> mtu 1428 qdisc noop state DOWN group default qlen 1000     link/ether 9e:4f:b4:97:b7:50 brd ff:ff:ff:ff:ff:ff 4: wlp4s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP group default qlen 1000     link/ether 48:45:20:0b:ec:9e brd ff:ff:ff:ff:ff:ff     inet 192.168.0.32/24 brd 192.168.0.255 scope global dynamic noprefixroute wlp4s0        valid_lft 85114sec preferred_lft 85114sec     inet6 fe80::2bd1:8f16:862:414d/64 scope link noprefixroute         valid_lft forever preferred_lft forever 5: br0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc noqueue state DOWN group default qlen 1000     link/ether 54:ee:75:92:1a:60 brd ff:ff:ff:ff:ff:ff 6: virbr0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc noqueue state DOWN group default qlen 1000     link/ether 52:54:00:f5:d4:70 brd ff:ff:ff:ff:ff:ff     inet 192.168.122.1/24 brd 192.168.122.255 scope global virbr0        valid_lft forever preferred_lft forever 7: virbr0-nic: <BROADCAST,MULTICAST> mtu 1500 qdisc fq_codel master virbr0 state DOWN group default qlen 1000     link/ether 52:54:00:f5:d4:70 brd ff:ff:ff:ff:ff:ff 

I believe this means I should use enp0s25 where the instructions use eth0 . This laptop does not have an ethernet port, which I believe is what the “eth” stands for.

Hence, I have edited my /etc/network/interfaces as follows:

sudo apt install qemu-kvm libvirt-clients libvirt-daemon-system bridge-utils virt-manager  /etc/network/interfaces  eth0 = enp0s25 

Then I made sure my user was in libvirt and libvirt-qemu groups with the following commands:

sudo adduser [username] libvirt sudo adduser [username] libvirt-qemu 

Those commands seemed to take just fine, so I rebooted the machine to make sure it took effect. It took longer to start up this time, so I assumed it was doing something.

Virtualization is enabled in the BIOS.

What did I do wrong?