netdev - Re: IP-Aliasing for IPv6?

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Date:   Mon, 20 May 2019 22:33:26 +0200
From:   Toke Høiland-Jørgensen <toke@...hat.com>
To:     "M. Buecher" <maddes+kernel@...des.net>, netdev@...r.kernel.org
Cc:     Michal Kubecek <mkubecek@...e.cz>,
        Matthias May <matthias.may@...atec.com>,
        Heiner Kallweit <hkallweit1@...il.com>
Subject: Re: IP-Aliasing for IPv6?

"M. Buecher" <maddes+kernel@...des.net> writes:

> On 2019-05-15 11:26, Michal Kubecek wrote:
>> On Tue, May 14, 2019 at 08:49:12PM +0200, M. Buecher wrote:
>>> According to the documentation [1] "IP-Aliasing" is an obsolete way to
>>> manage multiple IP[v4]-addresses/masks on an interface.
>>> For having multiple IP[v4]-addresses on an interface this is 
>>> absolutely
>>> true.
>>> 
>>> For me "IP-Aliasing" is still a valid, good and easy way to "group" ip
>>> addresses to run multiple instances of the same service with different 
>>> IPs
>>> via virtual interfaces on a single physical NIC.
>>> 
>>> Short story:
>>> I recently added IPv6 to my LAN setup and recognized that IP-Aliasing 
>>> is not
>>> support by the kernel.
>>> Could IP-Aliasing support for IPv6 be added to the kernel?
>> 
>> You should probably better explain what is the feature you are using
>> with IPv4 but you are missing for IPv6. The actual IP aliasing has been
>> removed in kernel 2.2, i.e. 20 years ago. Since then, there is no IP
>> aliasing even for IPv4. What exactly works for IPv4 but does not for
>> IPv6?
>
> Used feature is the label option of `ip`, which works for IPv4, but not 
> with IPv6.
>
> Goal: Use virtual interfaces to run separate instances of a service on 
> different IP addresses on the same machine.
> For example with dnsmasq I use `-interface ens192` for the normal main 
> instance, while using `-interface ens192:0` and `-interfaces ens192:1` 
> for special instances only assigned to specific machines via their MAC 
> addresses.

You would generally instruct your daemon to listen to an address rather
than an interface. For dnsmasq you can do this with the --listen-address
option instead of the --interface option, AFAIK.

-Toke