IPv4 is not showing, current Ubuntu build says "Failed to start Raise network interfaces"

Question

Hi, I have a droplet with IPv4 and IPv6 enabled. It has never been a problem. However, yesterday I somehow managed to break my droplet while upgrading. IPv6 looks fine but IPv4 is now missing from my IP if I run $ip addr .

I can access the DO console to test, but cannot ssh in or ping from my terminal.

$cat /etc/network/interfaces.d/* looks the same as an older snapshot (too old unfortunately). Changing network interfaces has yet to produce anything encouraging. My firewall is disabled. Not sure where else to look.

$sudo reboot shows the error: "Failed to start Raise network interfaces".

DO support has responded and recommended the following:

$ ip addr
learned that inet6 displays, inet not present

$ ip route
no change

$ ls -l /lib/modules
total 8
drwxr-xr-x 5 root root 4096 Jun 13 07:00 4.4.0-128-generic
drwxr-xr-x 5 root root 4096 Jul 2 13:51 4.4.0-130-generic

$iptables -nvL --line-numbers
empty

and lastly removing /etc/udev/rules.d/70-persistent-net.rules results in no change.

As per support I learned that IPv4 is not present. Support suggested “ensuring IPv4 is present” although I’m not sure how to go about accomplishing that.

Hopefully someone out here can throw me a bone, it has been a long night.

o1sound · Answer

I just had a rather enlightened colleague of mine solve this for me. Running $ifconfig or $ip addr, he saw how inet6 can be found but not inet (IPv4). On a hunch he opened network interfaces and commented out all IPv6 related lines as follows:

$ sudo nano /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 inet6 static
#       address ****:****:****:****:****:****:****:****
#        netmask 64
#        gateway ****:****:****:****:****:****:****:****
#        autoconf 0
#        dns-nameservers ****:****:****::**** ****:****:****::8888 8.8.8.8
iface eth0 inet static
        address ***.***.***.**
        netmask ***.***.***.*
        gateway ***.***.***.*
        up ip addr add 10.20.0.5/16 dev eth0

Running ifconfig we can now see there are now two inet6 and one inet. I don’t claim to know what happened here, but this new inet now allows me to ping my droplet! Websites are now up, and I can ssh into the droplet to backup as needed.

eth0      Link encap:Ethernet  HWaddr 04:01:35:48:9e:01  
          inet addr:***.***.***.*  Bcast:***.***.***.***  Mask::***.***.***.***
          inet6 addr: ****:****:***:**::***:****/64 Scope:Global
          inet6 addr: ****::***:****:****:****/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:44118 errors:0 dropped:0 overruns:0 frame:0
          TX packets:51888 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:9519589 (9.5 MB)  TX bytes:156384397 (156.3 MB)

This was a little scary for a while there! Happy to at least have this to work from.

alexdo · Answer

Hello there,

It is important to backup your droplet by taking snapshot or create a copy of the system files before going for a system update/upgrade. It seems like somehow the IPv6 configuration was affected and thus caused the issue for you.

You can always examine the default network interface for any syntax errors or misconfigurations.

We also have an article on how to diagnose issues with the network configuration.

https://docs.digitalocean.com/support/check-your-droplets-network-configuration/

Regards

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IPv4 is not showing, current Ubuntu build says "Failed to start Raise network interfaces"

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