I've got a VM running Ubuntu 18.04 - it's all setup and running on a single public IP and has two interfaces - ens160 (public) & ens192 (private).

My interface ens160 is already fully configured. However, when I try and setup ens192 and apply the settings with netplan apply, ens160 stops pinging externally.

ifconfig -

ens160: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet  netmask  broadcast
        inet6 fe80::250:56ff:feb2:ac74  prefixlen 64  scopeid 0x20<link>
        ether 00:50:56:b2:ac:74  txqueuelen 1000  (Ethernet)
        RX packets 8761053  bytes 3882588408 (3.8 GB)
        RX errors 0  dropped 242551  overruns 0  frame 0
        TX packets 10449256  bytes 4654699595 (4.6 GB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

ens192: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet6 fe80::250:56ff:feb2:3d74  prefixlen 64  scopeid 0x20<link>
        ether 00:50:56:b2:3d:74  txqueuelen 1000  (Ethernet)
        RX packets 242552  bytes 14553120 (14.5 MB)
        RX errors 0  dropped 227391  overruns 0  frame 0
        TX packets 7256  bytes 2349506 (2.3 MB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

lo: flags=73<UP,LOOPBACK,RUNNING>  mtu 65536
        inet  netmask
        inet6 ::1  prefixlen 128  scopeid 0x10<host>
        loop  txqueuelen 1000  (Local Loopback)
        RX packets 9194  bytes 2309681 (2.3 MB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 9194  bytes 2309681 (2.3 MB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

Here's the configuration file 50-cloud-init.yaml I'm attempting below -

                search: []
            optional: true
            optional: true
    version: 2

As soon as I run netplan try, I can no longer ping my external IP until the timeout and the network resets itself. Interestingly though, I can still ping the external IP from other VM's within the network - I'm not sure if that means anything?

The newly configured internal IP also begins pinging within the network - what I'd expect.

I hope you can help!


  • 3
    Don't set a gateway. You can only have one default gateway. – Zoredache Sep 4 '18 at 16:44
  • @Zoredache - and it was as simple as that! Sir - you are a legend! Please feel free to add as the answer :) – Chris Sep 4 '18 at 16:45
  • @Zoredache - just a quick question though - how come it doesn't need a second gateway considering it's a completely separate interface? – Chris Sep 4 '18 at 16:46

The problem is almost certainly related to you attempting to set a default gateway on the secondary interface.

It is important to always remember that the default gateway isn't really a property of an individual interface instead it is a route added to the route table. The 'default gateway' is the route that is used when no other more specific routes do not match a given destination. If you attempt to add two default gateways with the same metric, only one or the other will work.


The default gateway is the address of the router which will route packets for which you don't have routes defined already. About 99% of the time, this is the router which will provide your system access to the Internet. Any host will have exactly one of these (per protocol) in a normal configuration.

You've defined two, so one conflicts with and overrides the other. Because it is not your gateway to the Internet, you should remove it again.

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