+##finds last usable ip (broadcast minus 1) of a subnet from an IP and netmask
+## Warning: This function only works for IPv4 at the moment.
+##params: ip, netmask
+function find_last_ip_subnet {
+ IFS=. read -r i1 i2 i3 i4 <<< "$1"
+ IFS=. read -r m1 m2 m3 m4 <<< "$2"
+ IFS=. read -r s1 s2 s3 s4 <<< "$((i1 & m1)).$((i2 & m2)).$((i3 & m3)).$((i4 & m4))"
+ printf "%d.%d.%d.%d\n" "$((255 - $m1 + $s1))" "$((255 - $m2 + $s2))" "$((255 - $m3 + $s3))" "$((255 - $m4 + $s4 - 1))"
+}
+