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Re: IPv6 radvd questions




On Mon, Mar 26, 2018 at 08:25:56PM +1300, Richard Hector wrote:
> Hi all,
> 
> I'm getting a little confused by the radvd docs, and possibly by IPv6
> concepts in general ...
> 
> The router I'm configuring isn't the default gateway of the LAN; it's an
> openvpn endpoint (server), and I just want to advertise the routes
> available via tunnels to the LAN.
> 
> radvd's prefix blocks, if I understand correctly, are for telling other
> machines on the local network what range to use for SLAAC, right? Which
> is a job already being done by (multiple) other routers.
> 
> Given that, can I ignore the prefix blocks, and just include route blocks?

Yes.


> Will that be enough?

Almost. The problem is that Linux makes a preventative
assumption that only default routes will be advertised.
(At least, this used to be the case. I don't have a
currently running example.)

On each client, you will need to set a sysctl:
net.ipv6.conf.all.accept_ra_rt_info_max_plen = 128

to enable accepting those non-default routes.

Also note that your openvpn server will probably stop
listening to route advertisements once it is an IPv6 router,
and so you will either need to set the default route there
statically, or run a routing protocol like RIPng between
them. If this is your only internal router, I would recommend
static.

-dsr-