IP/CIDR Δ to last IP addr Mask Hosts (*) Class Notes
a.b.c.d/30 +0.0.0.3 255.255.255.252 4

(*) Note that for routed subnets bigger than /31 or /32, 2 needs to be subtracted from the number of available addresses - the largest address is (conventionally[citation needed]) used as the broadcast address, and typically the smallest address is used to identify the network itself. See RFC 1812 for more detail. It is also common for the gateway IP for that subnet to use an address, meaning that you would subtract 3 from the number of usable hosts that can be used on the subnet.
1 рабочий адрес!

НО если мы смаршртизируем подсеть 30 бит в наш рабочий адрес то он будет являтся шлюзом для нашей смаршрутизированной сети