Mod_geoip is an Apache module use for determination of City/Country/ISP of a visitor. In CentOS 6 mod_geoip is not available in the default set repository so you will need to download it manually.
wget http://download.fedora.redhat.com/pub/epel/6/x86_64/mod_geoip-1.2.5-5.el6.x86_64.rpm
rpm -ivh mod_geoip-1.2.5-5.el6.x86_64.rpm
/etc/init.d/httpd restart
Completed. You should see mod_geoip.conf under /etc/httpd/conf.d/
ls /etc/httpd/conf.d/mod_geoip.conf