Re: Debian 11: How to disable IPv6

[Tim Woodall <debianuser@woodall.me.uk>]

On Sat, 9 Jul 2022, Charles Curley wrote:

> On Sun, 10 Jul 2022 06:44:46 +0200 (CEST)
> local10 <local10@tutanota.com> wrote:
>
> > Jul 10, 2022, 00:51 by charlescurley@charlescurley.com:
> >
> > >  I do it in part by
> > > using my own resolver, BIND9, and having it return only IPv4
> > > addresses.
> >
> > How did you do it? I tried to start named with "-4" option to use
> > only ipv4 but it refused to start with that option, IIRC.
> >
> > Regards,
>
> My /etc/default/named looks like:
>
> #
> # run resolvconf?
> RESOLVCONF=no
>
> # startup options for the server
> OPTIONS="-4 -u bind"
>
>
> That should do it.
>
> But all that does is tell named to use IPv4. It will still return IPv6
> addresses. So maybe I'm wrong about returning only IPv4 addresses.
> Hmmm....
I was a bit surprised. I've never had to disable ipv6 where the only
public routes are ipv4. Do some people have a default route for ipv6
that doesn't work?

The default settings don't make it easy for radvd to publish anything
other than a /64 prefix and a default route.

I am using ipv6 but I think you need things like:

  AdvDefaultLifetime 0;
to stop radvd providing a default route and

echo 64 >/proc/sys/net/ipv6/conf/eth0/accept_ra_rt_info_max_plen
to allow other routes to be configured.

this can mess up your day if there is any risk of rogue RAs on the
network

Tim