début de réponse

j'ai trouvé un début de réponse qui me permet de contacter les service de mes VMs depuis l'hôte.

Here is what I do specifically for localhost forwarding:
iptables -t nat -A OUTPUT -m addrtype --src-type LOCAL --dst-type LOCAL -p tcp --dport 3306 -j DNAT --to-destination ip.ip.ip.ip
iptables -t nat -A POSTROUTING -m addrtype --src-type LOCAL --dst-type UNICAST -j MASQUERADE
sysctl -w net.ipv4.conf.all.route_localnet=1
Make sure you substitute ip.ip.ip.ip for your real public IP and also the --dport 3306 for the port you want to forward.
Finally run the sysctl command and also update your /etc/sysctl.conf
You can update sysctl.ctl to allow the routing of localhost with the following command:
echo "net.ipv4.conf.all.route_localnet=1" >> /etc/sysctl.conf
Now this all seems simple and good but it did take some research and hunting down. Be warned and understand that forwarding localhost/127.0.0.1 requires this method and the typical other examples do not work. Some examples of solutions that do not work with localhost:
iptables -t nat -A PREROUTING -p tcp --dport 3306 -j DNAT --to ip.ip.ip.ip:3306
iptables -t nat -A POSTROUTING -d ip.ip.ip.ip -j MASQUERADE
http://realtechtalk.com/iptables_how_to_forward_localhost_port_to_remote_public_IP-1788-articles

En utilisant l'IP de ma VM pour ip.ip.ip.ip

Maintenant, je n'ai aucune idée des conséquences en terme de sécurité.

Je continue de chercher pour l'utilisation d'un service d'une VM par une autre VM.