+.It Va BroadcastSubnet Li = Ar address Ns Op Li / Ns Ar prefixlength
+Declares a broadcast subnet. Any packet with a destination address falling into such a subnet will be routed as a broadcast (provided all nodes have it declared).
+This is most useful to declare subnet broadcast addresses (e.g. 10.42.255.255), otherwise
+.Nm tinc
+won't know what to do with them.
+.Pp
+Note that global broadcast addresses (MAC ff:ff:ff:ff:ff:ff, IPv4 255.255.255.255), as well as multicast space (IPv4 224.0.0.0/4, IPv6 ff00::/8) are always considered broadcast addresses and don't need to be declared.