Sort list of IP Addresses using LINUX/UNIX sort utility:

sort -t'.' -k 1,1 -k 2,2 -n -k 3,3 -k 4,4 1.txt

where
-t specifies field separator
-k specifies the field, on which sorting is happening

       -t, --field-separator=SEP
              use SEP instead of non-blank to blank transition

       -k, --key=POS1[,POS2]
              start a key at POS1, end it at POS2 (origin 1)

cat 1.txt
243.242.6.254
192.21.64.1
156.20.4.92
30.160.5.20
30.20.12.1
30.20.5.1

O/P;

30.20.5.1

30.20.12.1

30.160.5.20

156.20.4.92

192.21.64.1

243.242.6.254