Comment # 27 on bug 1158817 from Neil Rickert

>I don't believe that NAT would work without any masquerading rules. You say you don't use it, but it's configured. Try pinging 8.8.8.8.

% ping 8.8.8.8
PING 8.8.8.8 (8.8.8.8) 56(84) bytes of data.
64 bytes from 8.8.8.8: icmp_seq=1 ttl=56 time=12.8 ms
64 bytes from 8.8.8.8: icmp_seq=2 ttl=56 time=12.2 ms
64 bytes from 8.8.8.8: icmp_seq=3 ttl=56 time=12.5 ms
64 bytes from 8.8.8.8: icmp_seq=4 ttl=56 time=12.5 ms
^C
--- 8.8.8.8 ping statistics ---
4 packets transmitted, 4 received, 0% packet loss, time 3005ms
rtt min/avg/max/mdev = 12.250/12.526/12.819/0.230 ms

That ping was from within the virtual machine named "slack12" (and running Leap
15.2 Alpha).

>Would you do me the favor to try what I suggested in comment 17?

I can try that.  But I'm not clear on what that entails.  Do you want me to
uncomment that line mentioned in comment 2; reboot; check that networking is
now failing in virtual machines; then run the firewall command and see if that
fixes it?