Iptables

IPTABLES

Show tables:

iptables -vL -t filter
iptables -vL -t nat
iptables -vL -t mangle
iptables -vL -t raw
iptables -vL -t security

Only first two seems relevant. Clear them:

iptables -t filter -F
iptables -t nat -F
 

Set needed settings (we assumes here that local network port is 'enp_bond', and uplink port is 'em1'):

iptables -A INPUT -i lo -j ACCEPT
iptables -A INPUT -i enp_bond -j ACCEPT
iptables -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT
iptables -t nat -A POSTROUTING -o em1 -j MASQUERADE
iptables -A FORWARD -i em1 -o enp_bond -m state --state RELATED,ESTABLISHED -j ACCEPT
iptables -A FORWARD -i enp_bond -o em1 -j ACCEPT

Save rules and restart service:

iptables-save > /etc/sysconfig/iptables
systemctl enable iptables
systemctl start iptables