I got a Ubuntu Server 16.04 LTs, it's a VM on a ESX (VMware). This server was in dhcp config and it worked fine until today. (I know a server should be in static address but in my case, i don't really need to be static). Today, I restarted the server (the VM) and there is not more IPv4 for the server, only a IPv6.

I didn't change anything in the config, i will show you the differents files/configs that I think is usefull, if you need more just ask.

/etc/hosts

127.0.0.1       localhost
127.0.1.1       my_hostname

# The following lines are desirable for IPv6 capable hosts
::1     localhost ip6-localhost ip6-loopback
ff02::1 ip6-allnodes
ff02::2 ip6-allrouters

/etc/hostname

my_hostname

/etc/network/interfaces

# This file describes the network interfaces available on your system
# and how to activate them. For more information, see interfaces(5).

# The loopback network interface
auto lo
iface lo inet loopback

# The primary network interface
auto eth0
iface eth0 inet dhcp

output from ifconfig command

eth0      Link encap:Ethernet  HWaddr 00:50:56:94:d1:ae
          adr inet6: fe80::250:56ff:fe94:d1ae/64 Scope:Lien
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          Packets reçus:68852 erreurs:0 :0 overruns:0 frame:0
          TX packets:1120 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 lg file transmission:1000
          Octets reçus:5658008 (5.6 MB) Octets transmis:329017 (329.0 KB)

lo        Link encap:Boucle locale
          inet adr:127.0.0.1  Masque:255.0.0.0
          adr inet6: ::1/128 Scope:Hôte
          UP LOOPBACK RUNNING  MTU:65536  Metric:1
          Packets reçus:26990 erreurs:0 :0 overruns:0 frame:0
          TX packets:26990 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 lg file transmission:1
          Octets reçus:1997350 (1.9 MB) Octets transmis:1997350 (1.9 MB)

I try to release IPv4 dhclient -4 -r -v

Internet Systems Consortium DHCP Client 4.3.3
Copyright 2004-2015 Internet Systems Consortium.
All rights reserved.
For info, please visit https://www.isc.org/software/dhcp/

Listening on LPF/eth0/00:50:56:94:d1:ae
Sending on   LPF/eth0/00:50:56:94:d1:ae
Sending on   Socket/fallback

same for IPv6 dhclient -6 -r -v

Removed stale PID file
Internet Systems Consortium DHCP Client 4.3.3
Copyright 2004-2015 Internet Systems Consortium.
All rights reserved.
For info, please visit https://www.isc.org/software/dhcp/

Listening on Socket/eth0
Sending on   Socket/eth0

**And it block here**

I also tried to ask a nex IP after dhclient -4 -v

DHCPDISCOVER on eth0 to 255.255.255.255 port 67
...
No DHCPOFFERS received.
No working leases in persistent database - sleeping.

I know the IP address of the DHCP server, so I specified it, dhclient -4 -v -s IP_ADDRESS_DHCP_SERVER

DHCPDISCOVER on eth0 to IP_ADDRESS_DHCP_SERVER port 67
...
No DHCPOFFERS received.
No working leases in persistent database - sleeping.

I don't know what to do any more, I tried to disable IPv6 but I just don't get any IP after that. I don't get it, it worked fine yesterday…

If you have an idea, I take it !
Thanks