Debian QEMU/KVM bridged networking and VLAN

Sun, 25 Jul 2021 00:00:00 +0000

By default on every Linux distro after installing QEMU and libvirt two kinds of networking are available:

NAT: VM sits behind a NAT.
MACVTAP: without going into much details it acts more or less like a bridged network, except not really. One of the most annoying limitations is that host to guest communication and vice versa are not really working well. Other important things might be broken as well, like for example VRRP. This mode is good for quick and dirty testing but not really for a stable environment.

BRIDGED networking is also supported by libvirt but requires some manual work.
A possible networking schema could be the following:

Keepalived and libvirt MACVTAP network interfaces

Wed, 13 Jan 2021 00:00:00 +0000

Keepalived is a routing software written in C that can be used to setup load balancing and high availiability for Linux machines.

NOTE: hypervisor is Debian 10 (Buster) with libvirt and qemu/kvm, virtual machines also are Debian 10 (Buster).

Keepalived configuration

Install keepalived:

$ apt install keepalived

Install nginx, it will be use to check that keepalived is actually working:

$ apt install nginx
$ systemctl enable --now nginx

Configure keepalived:

$ vi /etc/keepalived/keepalived.conf
---
global_defs {
 enable_script_security # prevents tampering with the check script
 script_user root # defines which user runs the check script
}

vrrp_script chk_nginx {
 script "/opt/scripts/nginx-check.sh"
 interval 2 # run script every 2 seconds
 weight 2 # add 2 points if OK
}

vrrp_instance VI_1 {
 interface enp2s0 # interface to monitor
 virtual_router_id 51
 priority 101 # MASTER 101, BACKUP 100
 advert_int 1
 nopreempt # comment to not have the VIP go back to MASTER 
 # -> when it comes back online
 authentication {
 auth_type PASS
 auth_pass myPass # maximum 8 chars
 }
 virtual_ipaddress {
 10.10.0.12/24 # VIP (Virtual IP Address)
 }
 track_script {
 chk_nginx
 }
}

Also add a script to check if nginx is alive and well:

Libvirt on nagg.eu

Debian QEMU/KVM bridged networking and VLAN

Keepalived and libvirt MACVTAP network interfaces

Keepalived configuration