Linux CentOS - block ip range

iptables -A INPUT -s 192.243.55.00/24 -j DROP
service iptables save
service iptables restart

Zakaj imaš sintakso: 192.243.55.00/24 in ne 192.243.55.0/24

[root@localhost ~]# iptables -A INPUT -s 192.243.55.0/24 -j DROP
[root@localhost ~]# service iptables save
Saving firewall rules to /etc/sysconfig/iptables: [ OK ]
[root@localhost ~]# service iptables restart
Flushing firewall rules: [ OK ]
Setting chains to policy ACCEPT: filter mangle [ OK ]
Unloading iptables modules: [ OK ]
Applying iptables firewall rules: [ OK ]
Loading additional iptables modules: ip_conntrack_netbios_n[ OK ]
[root@localhost ~]# sudo iptables -L INPUT
....
DROP all -- 192.243.55.0/24 anywhere
DROP all -- 192.243.55.0/24 anywhere
[root@localhost ~]#