After a seemingly random amount of time I cannot access (ping/ssh/http) a KVM host but can access its guests from anywhere. Restarting the network doesn't fix it. Restarting the machine does. All machines & VMs have static IPs. The network is configured with systemd.network, not netplan, because thats how the hosting provider set it up.
On ubuntu 64 bit 18.04.2 I can set up a bridge with these files in /etc/systemd/network
[NetDev] Name=br0 Kind=bridge
[Match] Name=br0 [Network] Description=network interface on public network, with default route DHCP=no Address=x.x.x.x/24 Gateway=x.x.x.x IPv6AcceptRA=no NTP=ntp.ovh.net DNS=127.0.0.1 DNS=x.x.x.x DNS=x.x.x.x Gateway=x:x:x:ff:ff:ff:ff:ff [Address] Address=x:x:x::/64 [Route] Destination=x:x:x:ff:ff:ff:ff:ff Scope=link
[Match] Name=eno1 [Network] Bridge=br0
From the host I can ping out to its gateway and www.google.com but not 22.214.171.124. I can download files using apt or curl. So it has connectivity.
What should I do or check to reliably have access on the host ?