create database db;

use db;

CREATE TABLE `test` (

  `a` int(11) NOT NULL AUTO_INCREMENT,

  `b` bigint(20) DEFAULT NULL,

  PRIMARY KEY (`a`),

  KEY `idx_b` (`b`)

) ENGINE=InnoDB AUTO_INCREMENT=129033 DEFAULT CHARSET=latin1

for i in `seq 1 254` ; do for z in `seq 1 254` ; do echo "insert into test (b) values (INET_ATON('192.168.${i}.${z}'));" ; done ; done | mysql db

Database changed

mysql> explain select MIN(b) from test where b >= inet_aton('192.168.119.32')\G

*************************** 1. row ***************************

           id: 1

  select_type: SIMPLE

        table: NULL

         type: NULL

possible_keys: NULL

          key: NULL

      key_len: NULL

          ref: NULL

         rows: NULL

        Extra: Select tables optimized away

1 row in set (0.00 sec)

MariaDB [db]> explain select MIN(b) from test where b >= inet_aton('192.168.119.32')\G

*************************** 1. row ***************************

           id: 1

  select_type: SIMPLE

        table: test

         type: range

possible_keys: idx_b

          key: idx_b

      key_len: 9

          ref: NULL

         rows: 32545

        Extra: Using where; Using index

1 row in set (0.00 sec)