Configuring the Firewall to allow incoming DHCP requests

The default configuration on CentOS is to enable the firewall and allow both ICMP and SSH requests in. The DHCP server will not work until we enable the firewall. We will be using firewalld and the firewall-cmd utility to make this happen. The “firewall-cmd --list-all” option shows the default firewall that allows dhcpv6-client (not to be confused with dhcp server) and ssh. We will add the dhcp service (as opposed to its ports).

The following syntax adds the ports associated with dhcp permanently. The --permanent flag is important. If you fail to add this, the next time you reboot, your changes will be lost. Make sure you reload the firewall to invoke the change. List all the rules and make sure your dhcp service has been added.

1. As root enter the following commands:

    firewall-cmd --list-all
    firewall-cmd --add-service=dhcp --permanent
    firewall-cmd --reload
    firewall-cmd --list-all
   

2. Type exit twice to leave PuTTy

Next is Windows 10 DHCP Client