2.2.3.4. Assign Static Ports and Use iptables Rules
2.2.3.4. Assign Static Ports and Use iptables Rules All of the servers related to NIS can be assigned specific ports except for rpc.yppasswdd - the daemon that allows users to change their login passwords. Assigning ports to the other two NIS server daemons, rpc.ypxfrd and ypserv , allows for the creation of firewall rules to further protect the NIS server daemons from intruders. To do this, add the following lines to /etc/sysconfig/network : The following iptables rules can then be used to enforce which network the server listens to for these ports: This means that the server only allows connections to ports 834 and 835 if the requests come from the 192.168.0.0/24 network, regardless of the protocol. Note Refer to Section 2.8, "Firewalls" for more information about implementing firewalls with iptables commands.
YPSERV_ARGS="-p 834" YPXFRD_ARGS="-p 835" ~]# iptables -A INPUT -p ALL -s ! 192.168.0.0/24 --dport 834 -j DROP ~]# iptables -A INPUT -p ALL -s ! 192.168.0.0/24 --dport 835 -j DROP