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Linux CentOS 7 - Configuring a cache-only DNS

Linux CentOS 7 - Configuring a cache-only DNS

Configure a cache only DNS server which forwards requests to the well known Google DNS server.

On system1

Install the unbound package
# yum install -y unbound

Enable and start the service
# systemctl enable unbound && systemctl start unbound

Adjust the configuration file
# vim /etc/unbound/unbound.conf

interface: 0.0.0.0                       ## all interfaces
access-control: 0.0.0.0/0 allow ## from all networks
forward-zone
     name: "."                              ## from any domain
     forward-addr: 8.8.8.8           ## DNS server towards which all requests will be forwarded

Check configuration
 # unbound-checkconf

Modify the DNS server on the interface configuration
# vim /etc/sysconfig/network-scripts/ifcfg-ens33

DNS1: 192.168.189.140
DNS2: 8.8.8.8

Restart the network service
# systemctl restart network

Populate the cache
# ping cnn.com
# ping cisco.com
# ping juniper.net
# ping redhat.com
# ping centos.org

Check the cache has been populated
# dig cnn.com

Dump the cache
# unbound-control dump-cache

Save the cache in a file
# unbound-control dump-cache > cachefile

Load the cachefile into memory

# unbound-control dump-cache < cachefile

If you experience problems with this configuration, just let me know.

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