You can see the full instructions here: http://danscourses.com/install-centos-7-6-and-configure-it-as-a-firewall-gateway-router/

The lab was taken from my Winter 2015 Final Exam, it is a great project that I know you will love. I have updated it to work with CentOS7.

Instructions:

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CentOS7 Linux Router and Server
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Install Linux – 2pts
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A. Use the CentOS7 minimal install x86_64 iso image file. You can download it here: http://centos.org/

B. Using Virtualbox create a new virtual machine: Choose “I will install the operating system later.”
– Settings: Linux, RedHat 64 bit, Disk Size minimum 12Gb, Memory 1 to 2Gb
– Choose Settings: set the CD-ROM to boot directly from the CentOS-7 iso image file,
– Choose Settings: set the network adapter to bridged mode

C. Click finish and then Start which will boot the virtual machine to the iso image file. Install CentOS-7.5 (the latest version)

D. Important settings:

– Name your Centos localhost hostname: centos.yourname.local
– set the root password: yourchoice
– create a user account and password
– set the location timezone
– accept all other default settings

E. Login to CentOS7 as root and take a screenshot logged into your CentOS7 Virtual Machine (save screenshot)