ipv6 default router Operation not permitted

[Damien Fleuriot]

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

> On 2013/03/13 02:25, Damien Fleuriot wrote:
> 
> [...]
> 
>> 
>> 
>> The network is actually /48 and you get assigned a /64 inside it.
>> 
>> Set your interface to use the /48 prefix and voodoo will happen (I can assure 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 outside the /64 that was given you.
> 
> 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.
> 
> 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 
> to ACCEPT_RTADV. But that doesn't make immediate sense.
> 
> Corrections and education welcome.
> 
>> 
>> 
>> Kindly reply with topic "SOLVED" if that fixed you up, that googlers in the future may find the solution easily.
> 
> 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.
> 
> C.
> -- 


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

FreeBSD's hardly responsible here.

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


This is the same use case as getting A /29 assignment inside a /24, but having 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 and gives you the ability to reach the GW, just keep to your /64 for assignments ;)