Re: "unreachable" routes

[Robert Vogelgesang <vogel folz de>]

Hi Thomas,

think of this system as a VPN Access Concentrator.  "unreachable" routes
are used to avoid "ping-pong-storms" between this system and the gateway
for networks that currently aren't connected.  That's a simpler solution
than to use a dynamic routing protocol.

I think we'll go with "network-script", again for simplicity.

Thank you for your feedback.

Best,

Robert

On Mon, Feb 22, 2021 at 05:42:15PM +0100, Thomas Haller via networkmanager-list wrote:
> On Thu, 2021-02-18 at 12:28 +0100, Robert Vogelgesang wrote:
> > Hello @all,
> >
> > currently I'm trying to update an old server running CentOS 6, which
> > doesn't use NetworkManager, to a system with Networkmanager 1.26.0.
> > I'm strugging to find the correct syntax to define "unreachable"
> > routes.
> >
> > In CentOS 6 this could be done by creating a file, e. g.
> > /etc/sysconfig/network-scripts/route-eth0, with the content:
> >
> > unreachable 192.0.2.0/24 metric 3
> >
> > If I read
> >  
> > https://gitlab.freedesktop.org/NetworkManager/NetworkManager/-/blob/nm-1-26/src/settings/plugins/ifcfg-rh/nms-ifcfg-rh-reader.c
> > correctly, NM 1.26.0 should still support this syntax, but when I try
> > it, reading the interface configration fails, without any error
> > message.
> >
> > The nmcli man page doesn't mention "unreachable" or "blackhole"
> > routes.
> > nmcli does not accept this syntax when I try to set the ipv4.routes
> > property of a connection.
> >
> > Any hints?
>
> Hi,
>
> Currenlty, NetworkManager only supports "type=unicast" and "type=local"
> routes. It would be nice to add support for other route types.
>
> Anyway, as it is, the options are:
>
> (1) not use NetworkManager but a script/tool of your choice that works
> for you (like "network-script" from "initscripts" package).
>
> (2) use a dispatcher script, that would call `ip route add`. See `man
> NetworkManager`.
>
> (3) use "NetworkManager-dispatcher-routing-rules". That is basically a
> dispatcher script ([1]) which does what "network-scripts" do. You would
> configure the routes and rules in /etc/sysconfig/network-
> scripts/{rule,route}. I don't think this is the best solution. If you
> go with the dispatcher script way, then (2) is simple enough without
> requiring you to configure routes in ifcfg format.
>
>
> I would get inspired by (3) (see the script at [1]) and write a simple
> dispatcher script that works for you (2).
>
> [1] 
> https://gitlab.freedesktop.org/NetworkManager/NetworkManager/-/blob/e3a7f29e2af2acd6b03b313115396bb6872e3cd0/examples/dispatcher/10-ifcfg-rh-routes.sh
>
>
> Can you elaborate why you use "unreachable" routes? It's the first time
> I encounter somebody actually using this. Seems you hav specific
> requirements, and while NetworkManager should support them, I think it
> may be warranted that for now you roll your own special solution (that
> is, a script).
>
>
> best,
> Thomas



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