Zentyal as a firewall (gateway).

Zentyal is the Linux Small Business Server, it lets you manage all your network services through one single platform. It's a Network Gateway, as well as an Infrastructure, UTM (Unified Threat Manager), Office and Communications Server. All these features are fully integrated and easy to configure, it truly helps to save system administrators time.

In this LINK(tutorial), you will see how to set up a Zentyal Server to act as a gateway in a very common scenario. Zentyal will provide basic network infrastructure, load balancing between two Internet providers, firewall and HTTP proxy caching and content filtering. All these steps are well explained in the Zentyal Documentation, which is a really recommended reading.

Centos 7 firewall (firewalld)

Centos 7 is using firewalld instead of iptables. Below are the steps to enable/disable firewalld.

To check the status of the firewall:

#  service firewalld status 

To disable the firewall:

#  service firewalld stop 

To start the firewall:

#  service firewalld start 

To enable firewall on boot:

#  systemctl enable firewalld

To disable firewall on boot:

#  systemctl disable firewalld

To check on how to configure firewall:

#  man firewall-cmd

To get the default zone:

#  firewall-cmd --get-default-zone

To list all services in public zone:

#  firewall-cmd --zone=public --list-all

To accept http service in public zone permanently:

#  cat /etc/firewalld/zones/public.xml
#  firewall-cmd --permanent --zone=public --add-service=http
#  firewall-cmd --reload
#  cat /etc/firewalld/zones/public.xml

To deny http service in public zone permanently:

#  cat /etc/firewalld/zones/public.xml
#  firewall-cmd --permanent --zone=public --remove-service=http
#  firewall-cmd --reload
#  cat /etc/firewalld/zones/public.xml

The GUI screen to control the firewall is available from the menu.

To install using yum:

# yum install firewall-config

To get to Firewall GUI:

Fedora : System > Administration > Firewall
RHEL7/OL7 : Applications > Sundry > Firewall