Ok, thanks for your answer.
But what happens if I want to set up a private dynamic network for my VPS? Is it still possible to set up a DNS server and a DHCP server (with dnsmasq for example) with this configuration?
I have tried previously without any success, I don't know if the problem comes from this configuration. I had this in the file /etc/network/interfaces of the VPS:
# Auto generated interfaces
auto lo
iface lo inet loopback
auto venet0
iface venet0 inet static
address 127.0.0.1
netmask 255.255.255.255
broadcast 0.0.0.0
up route add -net 192.0.2.1 netmask 255.255.255.255 dev venet0
up route add default gw 192.0.2.1
auto venet0:0
iface venet0:0 inet dhcp
Thank you for your help!