FreeBSD 8 as an IPv6 router

[Mattia Rossi]

On 14/12/11 04:07, Hajimu UMEMOTO wrote:
> Hi,
>
>>>>>> On Tue, 13 Dec 2011 20:11:45 +1030
>>>>>> "Daniel O'Connor"<doconnor at gsoft.com.au>  said:
>
> doconnor>  On 13/12/2011, at 19:54, Hajimu UMEMOTO wrote:
>> doconnor>  Is there a way to tweak it to do the right thing?
>>
>> Perhaps, sla-len should be 8.
>
> doconnor>  Ahh many thanks, that seems work work.
>
> You are welcome.
>
> doconnor>  Such are the risk when you copy things off the internet :)
>
> Yes, the sla-len depends on the prefixlen of the delegated prefix, and
> the length depends on your ISP.
> The DHCPv6 server announces the prefixlen, and the dhcp6c can know it.
> However, the dhcp6c doesn't assume that the prefixlen of the
> prefix-interface is 64.  So, you still need to specify an appropriate
> sla-len value.  It seems inconvenient to me.  So, I applied the
> attached patch to calculate the sla-len automatically with the
> assumption that the prefix-interface is 64, personally.
>

Ok, this is something I always get a bit confused with. I understand 
that it's the right clean thing to set up a /64 on the interface which 
sends router advertisements, but I also would expect by nature, that 
whatever prefixlength you chose on the interface, rtadvd would simply 
grab the lowest /64 prefix out of the configured one to send router 
advertisements out.

The idea there is, that you might use this router for multiple subnets, 
and have a single default route.

Now of course to do that you'd need to configure rtadvd.conf, so I guess 
the whole thing missing here is a bit of documentation which says, that 
if you don't configure rtadvd via rtadvd.conf you're not allowed to be 
lazy and configure any prefix on the interface and expect rtadvd to do 
the right thing.

It seems to me, that a lot of people (including me) would expect that, 
so maybe some info about that wouldn't be to bad.

Just my 2c.

Mat