[Dnsmasq-discuss] Both IPv6 router + separate dnsmasq server do router advertisements - results in two IPv6 routes for clients

[Geert Stappers]

On Sun, Feb 11, 2024 at 03:17:33PM +0100, Klaus Wissmann via Dnsmasq-discuss wrote:
> Hi all,
> 
> I’m pretty sure I’m overlooking something really simple
> but somehow I’m stuck.

     :-)

 
> Initially I had a fairly standard setup: my router at home does IPv6
> router advertisements + DHCP + DNS etc., local hosts do slaac and
> stateless dhcpv6.
> 
> Due to several reasons I wanted to move DHCP + DNS away from the router
> to a separate server. So what I did was
> • Switch off DHCPv6 on the router
> • Keep Router Advertisements active on router (with O flag set)
> • Set up dnsmasq on the new dedicated DNS/DHCP server (Debian 11, dnsmasq 2.85).
} go visit "paste bin"

Not visited

 
> What is now happening is that both the router as well as the dnsmasq
> server send router advertisements and my local hosts end up with two
> default routes. If I completely leave out the dhcp-range statement
> for IPv6, then dnsmasq will not send any router advertisements but
> unfortunately the really nice ra-names functionality is also switched
> off.

ra-names

I thought that was a made-up name,
but I found it also in the manual page of dnsmasq.

 
> Interestingly enough, my local Linux and MacOS don’t seem to be
> bothered at all by the two default routes while the Windows clients
> get confused sometimes (if I understand correctly depending on when
> they received which router advertisement).
> 
> I tried to dig into the source code a bit and if I prevent dnsmasq
> from executing send_ra_aliases() that seems to do the trick. But I
> have to admit that I don’t understand the source code thoroughly
> enough and I assume this will break something else...
> 
> So my question is: is there a way to stop dnsmasq from sending
> router advertisements while at the same still providing the ra-names
> functionality?

Consider to share information on the various attempts.


Regards
Geert Stappers
Not willing to answer yes-no-questions
-- 
Silence is hard to parse