Please turn off your firewall to start.
OLD WAY (For legacy distro's, this may be your case)
chkconfig iptables off
service iptables stop
NEW WAY (for recent distro's)
systemctl disable firewalld
systemctl stop firewalld
What we are looking for is a clean ACCEPT/ACCEPT/ACCEPT for INPUT/OUTPUT/FORWARD chains. This is a sledgehammer approach but what I prefer to start with instead of chasing our tails, otherwise 'just use CentOS' as it is SUPER SIMPLE there to get this working, gluster native client and all or NFS.