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Date:      Wed, 13 Mar 2013 12:16:27 +0100
From:      Damien Fleuriot <ml@my.gd>
To:        Schrodinger <schrodinger@konundrum.org>
Cc:        "freebsd-net@freebsd.org" <freebsd-net@freebsd.org>
Subject:   Re: ipv6 default router Operation not permitted
Message-ID:  <B04CE0AC-9917-4D3E-9159-99D6C7095B87@my.gd>
In-Reply-To: <20130313091727.GA17859@defiant.konundrum.org>
References:  <20130312225018.GA13589@defiant.konundrum.org> <3ABB5AED-DEA9-42F6-82A1-FEA9E8BBBDCF@my.gd> <20130313091727.GA17859@defiant.konundrum.org>

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On 13 Mar 2013, at 10:17, Schrodinger <schrodinger@konundrum.org> wrote:

> On 2013/03/13 02:25, Damien Fleuriot wrote:
>=20
> [...]
>=20
>>=20
>>=20
>> The network is actually /48 and you get assigned a /64 inside it.
>>=20
>> Set your interface to use the /48 prefix and voodoo will happen (I can as=
sure you with a 97% certainty that your default GW is inside the /48).
>> Of course, using the /48 prefix doesn't mean you can/may use IPs from out=
side the /64 that was given you.
>=20
> Voodoo, indeed... I'm sure there's a /48 used somewhere but to be more
> specific, or rather obvious, my default gateway resides at the boundary
> of a /56 - 2001:41D0:2:E700::/56 If you pay close attention you will
> notice that the default gateway is the last usable address from that
> range. I had already tried this btw, I spent some time confirming what I
> am was seeing; what was the actual case and ways I could perhaps change
> the configuration to get it Just Working. However, I would rather it
> worked correctly and not contain a configuration option that I either do
> not understand it's necessity nor do I see it as necessary.
>=20
> I don't claim to know IPv6 inside and out but one consideration I had
> was that because of the host route for the default gateway FreeBSD does
> not solicit for the "on-link gateway" because the interface is not set=20
> to ACCEPT_RTADV. But that doesn't make immediate sense.
>=20
> Corrections and education welcome.
>=20
>>=20
>>=20
>> Kindly reply with topic "SOLVED" if that fixed you up, that googlers in t=
he future may find the solution easily.
>=20
> I would, but IMO this isn't the most optimal solution; changing my
> prefix length so that I can reach the gateway... Can this kind of host
> routing just not be done ? The way I see this issue is that without
> ACCEPT_RTADV on my interface FreeBSD won't attempt Neighbour
> Solicitation for the default gateway but I am uncertain why this is the
> case. Bug or policy or That's How It Works.
>=20
> C.
> --=20


The thing is, your gateway sitting there in the middle of a /48 or /56 has t=
o do with how OVH distributes IPv6 prefixes and how they configure their rou=
ters.

FreeBSD's hardly responsible here.

I've had the very same problem with the very same host, hence why I immediat=
ely pointed out using a smaller prefix.


This is the same use case as getting A /29 assignment inside a /24, but havi=
ng to use /24 anyway because the host:
- doesn't want to bother configuring a gateway for each customer within its /=
24 (likely the case with ipv6)
- doesn't want to waste IPs (likely the case with ipv4)


Using a smaller prefix of /56 effectively puts you in the correct network an=
d gives you the ability to reach the GW, just keep to your /64 for assignmen=
ts ;)=



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