(switching back to -247.2 solves all the problems) I use Shorewall. On new systemd if I add any network interface (Tinc tap in my system) or switch network interface off (ip l s wan down), than up - _all_ the network disappears (I have lan and wan physical interfaces). Nothing changes in iptables nor "ip a" output but I cannot ping router connected directly to wan interface because of "Network unreachable"! (interfaces are still in UP state!) # ip r a default via 192.168.1.1 dev wan Error: Nexthop has invalid gateway I have to stop shorewall (policies stay DROP), turn up iface, add route (it does not appear automatically on -248) then start shorewall and now all the interfaces work until I remove or add any of them. It may cause serious problems when somebody will restart remote host after upgrade to systemd-248 and will face with same behaviour...
Are you using systemd-networkd? If so, what does your configuration look like? I don't know what "Tinc tap" means. I don't use shorewall or iptables in general, so you'll have to provide very specific information for anything to happen with this bug report. You might be better off working with shorewall/systemd upstream.