Why Can’t I Set a Static IP Address for My Linux Box?


I'm trying to set up a static local IP address for my Linux computer for port-forwarding purposes. As per every single guide that exists on this subject, I've edited my /etc/network/interfaces and /etc/resolv.conf files accordingly. However, upon rebooting, any changes I've made to resolv.conf are erased and the file is blank (except for the comment that warns me of exactly that).

As a result, I'm unable to resolve hostnames (ping google.com fails, for example). In fact, I can't even ping valid IP addresses ("Destination Host Unreachable").

Although ifconfig seems to reflect all the settings I put in /etc/network/interfaces, I am unable to access the Internet whatsoever, nor can I access the machine using SSH or FTP from another machine.

Here's my /etc/network/interfaces:

# interfaces(5) file used by ifup(8) and ifdown(8)
auto lo
iface lo inet loopback

auto eth0
iface eth0 inet static

Here's what ifconfig gives me:

eth0      Link encap:Ethernet  HWaddr 00:25:90:57:7c:65
          inet addr:  Bcast:  Mask:
          UP BROADCAST MULTICAST  MTU:1500  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:0 (0.0 B)  TX bytes:0 (0.0 B)
          Interrupt:20 Memory:fba00000-fba20000

eth1      Link encap:Ethernet  HWaddr 00:25:90:57:7c:64
          inet addr:  Bcast:  Mask:
          inet6 addr: fe80::225:90ff:fe57:7c64/64 Scope:Link
          RX packets:252 errors:0 dropped:0 overruns:0 frame:0
          TX packets:106 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:54010 (54.0 KB)  TX bytes:15731 (15.7 KB)
          Interrupt:16 Memory:fb900000-fb920000

lo        Link encap:Local Loopback
          inet addr:  Mask:
          inet6 addr: ::1/128 Scope:Host
          UP LOOPBACK RUNNING  MTU:65536  Metric:1
          RX packets:94 errors:0 dropped:0 overruns:0 frame:0
          TX packets:94 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0
          RX bytes:8088 (8.0 KB)  TX bytes:8088 (8.0 KB)

Why is this happening and how can I fix it?

Best Answer

If you are using a desktop version of Ubuntu, with a graphical network-manager tool installed, then you should not define the connection in the /etc/network/interfaces file.

Instead, open the connection via the nm-applet on the desktop (or by invoking nm-connection-editor from a terminal), navigate to the IPv4 settings tab, and set the connection mode to Manual using the drop-down selection box. Then add your desired IP and DNS settings in the boxes provided.

You should then revert any edits to your /etc/network/interfaces file (so that it contains only the lo definition lines) and either restart both the networking and network-manager services or reboot the machine.

You should also make sure that the chosen static IP address is outside the DHCP pool assigned by your router - in fact, you may find it simpler to keep a DHCP configuration on the machine, and reserve a particular IP for it on the router, if it supports DHCP address reservation.

If you really want to keep the GUI network-manager, but define your interface via /etc/network/interfaces, then you could try editing /etc/NetworkManager/NetworkManager.conf, changing




and then making sure there are no other competing connections defined in the /etc/NetworkManager/system-connections/ directory (where 'competing' means 'using the same interface as'). This should allow you to see and control the connections in /etc/network/interfaces under the GUI network-manager applet.

Alternatively you could remove the network-manager package altogether.

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