Not every uplink service implements BCP38. When putting up servers connected more-or-less directly to the Internet through these uplinks, it would be nice if the servers themselves were able to implement ingress and egress filtering according to BCP38. (Sorry about the typo in the subject lines of my previous message -- not everyone can get a BGP feed.) (Or, when using Ubuntu server edition to implement edge routers.) My earlier query was asking if anyone has encoded the blackhole routes in YAML for inserting in netplan(5). My prior message contains the routes to be blackholed. That takes care of egress routing. (I think I can write a Python program to take my list and convert it to the YAML that netplan(5) wants to see. That way, the routes are inserted when the public interface is up, and removed when the public interface is down.) Ingress routing appears to be one-line addition. IPTABLES can be told to weed out packets with unroutable source addresses. My experiments will add something like this line to the firewall: # iptables -A INPUT -m addrtype -i enp1s0 --src-type BLACKHOLE -j DROP THIS HAS NOT BEEN VERIFIED. I'm building a web server that will integrate this idea, and try it out.