==== Enable IP Forwarding First ====
<code>
sed -i 's/.*net\.ipv4\.ip_forward.*/net.ipv4.ip_forward = 1/' /etc/sysctl.conf
sysctl -p
</code>

==== NAT using iptables ====

=== Recommended Way (If IP is static) ===
<code>
iptables -t nat -A POSTROUTING -s 10.0.0.0/8 -j SNAT --to-source <IP>
</code>

=== Another Way (OpenVZ won't work this way) ===
<code>
iptables -t nat -A POSTROUTING -s 10.0.0.0/8 -j MASQUERADE
</code>

Or if you want to MASQUERADE all interfaces:
<code>
iptables -t nat -A POSTROUTING ! -o lo -j MASQUERADE
</code>