Setting up a Cache-only DNS Nameserver

• Different DNS Server Roles
• Primary (master) Nameserver
• Secondary (slave) Nameserver
• Cache only Nameserver
• Resource Records
• A: name to IP address
• AAAA: name to IPV6 address
• CNAME: Canonical Name; Alias
• PTR: Reverse DNS Resolution
• NS: Name Server; which name server is authoritative
• SOA: Start of authority; generic information about a domain
• MX: Mail Exchange that is responsible for this domain
• TXT: Supplies additional data, such as data that is used by sender policy framework networks and related
• SRV: Hosts that provide a specific service

• Setting up a Cache-only DNS Nameserver
• yum -y install unbound
• systemctl enable unbound
• systemctl start unbound
• vim /etc/unbound/unbound.conf
•  interface: 0.0.0.0        <-- allow all interface
•  access-control: 0.0.0.0/0 allow <-- allow everybody to queries
• forward-zone:
• name: "."   <-- forward zone for root
• forward-addr: 8.8.8.8. <-- DNS forward server
• Check config
• unbound-checkconf <-- check for syntax error only.

[root@server1 ~]# unbound-checkconf
unbound-checkconf: no errors in /etc/unbound/unbound.conf

• restart unbound
• systemctl restart unbound
• check status
• systemctl status -l unbound
• Add DNS to firewalld
• firewall-cmd --permanent --add-service=dns
• firewall-cmd --reload