Re: P.S. Re: Debian 9 in a VM with Proxmox 5 system

[Luca Filipozzi <lfilipoz@debian.org>]

I have dropped debian-devel@lists.debian.org.
I have added debian-user@lists.debian.org.

In previous emails, Maximilian complaned that Debian 9 had no 'route'
command. Having been advised to use 'ip route', he has offered this
snippet from this interfaces file for discussion.

On Mon, Jul 10, 2017 at 02:53:23PM +0200, Maximilian Althaus wrote:
> This is the config for (/etc/network/interfaces)
> 
> auto lo
> iface lo inet loopback
> 
> auto ens18
> allow-hotplug ens18
> iface ens18 inet static
>     addressIP.V4.ADDR.ESS
>     netmask 255.255.255.255
>     broadcastIP.V4.ADDR.ESS
>     post-up route addROOTER.IPV4.ADDR.ESSdev ens18
>     post-up route add default gwROOTER.IPV4.ADDR.ESS
>     pre-down route delROOTER.IPV4.ADDR.ESSdev ens18
>     pre-down route del default gwROOTER.IPV4.ADDR.ESS

Maximilian, why are you using 'route' in those post-up and pre-down
directives?

If you're going to use post-up and pre-down, then they need to be more
like (untested) the following, using 'ip route':

    post-up ip route add A.B.C.D dev ens18
    post-up ip route add default via A.B.C.D
    pre-down ip route del default via A.B.C.D
    pre-down ip route del A.B.C.D dev ens18

More importantly, why are you using post-up and pre-down directives to
add default routing? Is there a reason why your netmask is
255.255.255.255?

Assuming that you're on a /24 subnet (meaning, the netmask is
255.255.255.0), then try something like this, instead:

auto ens18
iface ens18 inet static
    address IP.V4.ADDR.ESS
    netmask 255.255.255.0
    gateway ROOTER.IPV4.ADDR.ESS

-- 
Luca Filipozzi