Before I re-invent the wheel, has anyone come up with blackhole route specifications for netplan in Ubuntu servers? Such a capability would perform the egress blocking for an edge server. The table of blackhole routes I would set up: IPv4 Address block Scope Description 0.0.0.0/8 Software Current network (only valid as source address). 10.0.0.0/8 Private network Used for local communications within a private network. 100.64.0.0/10 Private network Shared address space[3] for communications between a service provider and its subscribers when using a carrier-grade NAT. 127.0.0.0/8 Host Used for loopback addresses to the local host. 169.254.0.0/16 Subnet Used for link-local addresses between two hosts on a single link when no IP address is otherwise specified, such as would have normally been retrieved from a DHCP server. 172.16.0.0/12 Private network Used for local communications within a private network. 192.0.0.0/24 Private network IETF Protocol Assignments. 192.0.2.0/24 Documentation Assigned as TEST-NET-1, documentation and examples. 192.88.99.0/24 Internet Reserved. Formerly used for IPv6 to IPv4 relay 192.168.0.0/16 Private network Used for local communications within a private network. 198.18.0.0/15 Private network Used for benchmark testing of inter-network communications between two separate subnets. 198.51.100.0/24 Documentation Assigned as TEST-NET-2, documentation and examples. 203.0.113.0/24 Documentation Assigned as TEST-NET-3, documentation and examples. 224.0.0.0/4 Internet In use for IP multicast. 240.0.0.0/4 Internet Reserved for future use. 255.255.255.255/32 Subnet Reserved for the "limited broadcast" destination address. IPv6 Address block Usage Purpose ::/0 Routing Default route. ::/128 Software Unspecified address. ::1/128 Host Loopback address to local host. ::ffff:0:0/96 Software IPv4 mapped addresses. ::ffff:0:0:0/96 Software IPv4 translated addresses. 64:ff9b::/96 Global Internet IPv4/IPv6 translation. 100::/64 Routing Discard prefix. 2001::/32 Global Internet Teredo tunneling. 2001:20::/28 Software ORCHIDv2. 2001:db8::/32 Documentation Addresses used in documentation and example source code. 2002::/16 Global Internet The 6to4 addressing scheme fc00::/7 Private network Unique local address. fe80::/10 Link Link-local address. ff00::/8 Global Internet Multicast address.