Ubuntu – DHCP server only works one time


I installed e configured the DHCP server and removed all network-manager*.

All my settings are just like this one:
dhcpd fails to start on eth1
(but i use eth0)

I do:

sudo ifdown eth0
sudo ifup eth0

Then plug the cable between the server and the client.
The client receives the correct IP address: 192-168.0.50

BUT, if I unplug the cable and put it back the Client doesn't receive a valid IP address.
I have to make sudo ifdown eth0, sudo ifup eth0 at the server to the client receive a valid IP address again.

How do I fix this?

EDIT: my current configuration files are:

$ cat /etc/default/isc-dhcp-server


$ cat /etc/dhcp/dhcpd.conf
ddns-update-style none;

default-lease-time 600;
max-lease-time 7200;

subnet netmask {
  interface eth0;
  option subnet-mask;
  option broadcast-address;
  option routers;


$ cat /etc/network/interfaces
auto eth0
iface eth0 inet static


$ cat /etc/resolv.conf

I'm not using any router or switch. Just two PCs connected my cable.
After rebooting the server, i have to

$ sudo isc-dhcp-server start

After this the client PC obtains a correct IP.
BUT if I unplug the cable and connect it again, it won't get an IP in the correct range.
I have to ifdown and then ifup eth0.

Best Answer

  • If you removed or disabled NetworkManager you need to configure networking manually.

    1) Add your nameserver in /etc/resolv.conf

    # change '' to the nameserver you want to use.

    2) Bring your network down.

    sudo service networking stop

    3) Edit /etc/network/interfaces

    # command line
    sudo -e /etc/network/interfaces
    # graphical
    gksu gedit /etc/network/interfaces

    Add in your configuration for eth0. With DHCP it is short.

    auto eth0
    iface eth0 inet dhcp

    4) Bring your network up

    sudo service networking start

    dhcp / networking should then work properly when you re-boot.

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