Tjyylli

I am trying to set up 2 ip addresses on interface enp0s25. I am using 3 right now just for troubleshooting purposes.

Here is my setup
this is the content of /etc/network/interfaces.d/enp0s25

auto enp0s25

auto enp0s25:0

auto enp0s25:1



iface enp0s25 inet static

      address 192.168.1.95

      netmask 255.255.255.0

      gateway 192.168.1.1

      dns-nameservers 8.8.8.8 8.8.4.4



iface enp0s25:0 inet static

      address 192.168.1.96

      netmask 255.255.255.0

      gateway 192.168.1.1

      dns-nameservers 8.8.8.8 8.8.4.4



# This is the actual second ipaddress that I want

iface enp0s25:1 inet static

      address 172.16.28.250

      netmask 255.255.255.0

      gateway 172.16.28.1

      dns-nameservers 8.8.8.8 8.8.4.4

This is the contents of /etc/interfaces

# This file describes the network interfaces available on your system

# and how to activate them. For more information, see interfaces(5).



source /etc/network/interfaces.d/*



# The loopback network interface

auto lo

iface lo inet loopback



# The primary network interface

allow-hotplug enp0s25

# iface enp0s25 inet dhcp

When I do a sudo service network restart it fails
so then I do sudo service network status and I get

● networking.service - Raise network interfaces

   Loaded: loaded (/lib/systemd/system/networking.service; enabled; vendor preset: enabled)

   Active: failed (Result: exit-code) since Mon 2019-02-25 15:15:37 EST; 3min 8s ago

     Docs: man:interfaces(5)

  Process: 481 ExecStart=/sbin/ifup -a --read-environment (code=exited, status=1/FAILURE)

  Process: 477 ExecStartPre=/bin/sh -c [ "$CONFIGURE_INTERFACES" != "no" ] && [ -n "$(ifquery --read-environment --lis

 Main PID: 481 (code=exited, status=1/FAILURE)



Feb 25 15:15:37 trmi-ral-server systemd[1]: Starting Raise network interfaces...

Feb 25 15:15:37 trmi-ral-server ifup[481]: RTNETLINK answers: File exists

Feb 25 15:15:37 trmi-ral-server ifup[481]: ifup: failed to bring up enp0s25:0

Feb 25 15:15:37 trmi-ral-server ifup[481]: RTNETLINK answers: File exists

Feb 25 15:15:37 trmi-ral-server ifup[481]: ifup: failed to bring up enp0s25:1

Feb 25 15:15:37 trmi-ral-server systemd[1]: networking.service: Main process exited, code=exited, status=1/FAILURE

Feb 25 15:15:37 trmi-ral-server systemd[1]: Failed to start Raise network interfaces.

Feb 25 15:15:37 trmi-ral-server systemd[1]: networking.service: Unit entered failed state.

Feb 25 15:15:37 trmi-ral-server systemd[1]: networking.service: Failed with result 'exit-code'.

but if I restart, then they work.

ip address shows them all assigned.

I can ping them from another computer on both networks (swapping the ethernet cable between them)

But, service networking status still shows that it is failed.

how can I have networking not running but actually have network connectivity?

service networking status still shows that it is failed.

The program doesn't tell you, but the failure message has nothing to do with your addresses; it is actually failing because you told it to configure the same route twice.

Yes, you can have two routes for the same network as long as they go over different interfaces. But you don't really have different interfaces; all you have is 3 entries for the same "enp0s25" interface. There is no such thing as "alias interfaces".

So your configuration file translates to these commands:

ip addr add 192.168.1.95/24 dev enp0s25

ip route add 0.0.0.0/0 via 192.168.1.1 dev enp0s25



ip addr add 192.168.1.96/24 dev enp0s25

ip route add 0.0.0.0/0 via 192.168.1.1 dev enp0s25



ip addr add 172.16.28.250/24 dev enp0s25

ip route add 0.0.0.0/0 via 172.16.28.1 dev enp0s25

Notice that the configuration asks the route for 0.0.0.0/0 ... dev enp0s25 to be added twice. The first attempt succeeds and gives you connectivity, the second attempt fails and crashes ifupdown (networking.service), the third attempt would do the same as well.

To avoid this, remove all gateway... lines except one.

(Note: Linux, by default, does not support per-subnet IPv4 gateways – if you add multiple default routes, it will just pick one and use it for everything, even if it's for the "wrong" subnet. So if 192.168.1.1 and 172.16.28.1 belong to the same router, you don't actually need to add both.)

The file, updated for Debian 9 syntax, would look like:

auto enp0s25



iface enp0s25 inet static

      address 192.168.1.95/24

      gateway 192.168.1.1

      dns-nameservers 8.8.8.8 8.8.4.4



iface enp0s25 inet static

      address 192.168.1.96/24



iface enp0s25 inet static

      address 172.16.28.250/24

how can I have networking not running but actually have network connectivity?

It's never "running" in the first place. It's just a script that configures the IP addresses and exits, and that's all it does. The network is handled entirely by the Linux kernel itself.