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IPv6 addresses

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  IPv6 addresses Richard Hector <richard@walnut.gen.nz> - 2019-02-07 10:10 +0100
    Re: IPv6 addresses Richard Hector <richard@walnut.gen.nz> - 2019-02-07 10:20 +0100
      Re: IPv6 addresses Pascal Hambourg <pascal@plouf.fr.eu.org> - 2019-02-07 20:10 +0100
        Re: IPv6 addresses Dan Ritter <dsr@randomstring.org> - 2019-02-07 20:40 +0100
          Re: IPv6 addresses Richard Hector <richard@walnut.gen.nz> - 2019-02-08 04:10 +0100
        Re: IPv6 addresses Richard Hector <richard@walnut.gen.nz> - 2019-02-08 04:10 +0100
          Re: IPv6 addresses Pascal Hambourg <pascal@plouf.fr.eu.org> - 2019-02-08 19:50 +0100

#205084 — IPv6 addresses

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Hi all,

Tipped off by a comment on here, and confirmed I think by reading the
manpage, it seems I should be able to set multiple addresses on an
interface by using multiple iface stanzas for the same interface in
/etc/network/interfaces.

So I have something like this:

iface ens3 inet static
  <v4 stuff>

# this one should hopefully configure via SLAAC
iface ens3 inet6 auto

# this one is for my static stuff (using a ULA prefix)
iface ens3 inet6 static
  address 2001:db8::1/64
  up ip -6 route add ...
  up ip -6 route add ...
  up ip -6 route add ...

But I don't get the SLAAC address. The only way I've managed to get the
SLAAC address plus the static, is to have a single auto stanza like this:

iface ens3 inet6 auto
  up ip -6 addr add 2001:db8::1/64 dev ens3
  up ip -6 route add ...
  up ip -6 route add ...
  up ip -6 route add ...

Incidentally, that also gives me an autoconfigured address (based on the
MAC) in the 2001:db8::/64 prefix, which I don't think I need.

Does that suggest a bug in ifupdown? Or am I interpreting something wrong?

Cheers,
Richard

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#205087

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On 7/02/19 10:05 PM, Richard Hector wrote:
> Hi all,
> 
> Tipped off by a comment on here, and confirmed I think by reading the
> manpage, it seems I should be able to set multiple addresses on an
> interface by using multiple iface stanzas for the same interface in
> /etc/network/interfaces.
> 
> So I have something like this:
> 
> iface ens3 inet static
>   <v4 stuff>
> 
> # this one should hopefully configure via SLAAC
> iface ens3 inet6 auto
> 
> # this one is for my static stuff (using a ULA prefix)
> iface ens3 inet6 static
>   address 2001:db8::1/64
>   up ip -6 route add ...
>   up ip -6 route add ...
>   up ip -6 route add ...
> 
> But I don't get the SLAAC address. The only way I've managed to get the
> SLAAC address plus the static, is to have a single auto stanza like this:
> 
> iface ens3 inet6 auto
>   up ip -6 addr add 2001:db8::1/64 dev ens3
>   up ip -6 route add ...
>   up ip -6 route add ...
>   up ip -6 route add ...
> 
> Incidentally, that also gives me an autoconfigured address (based on the
> MAC) in the 2001:db8::/64 prefix, which I don't think I need.
> 
> Does that suggest a bug in ifupdown? Or am I interpreting something wrong?

Actually, if I put the 'auto' stanza after the 'static' one, it does
work (I still get the autogenerated address in the ULA prefix).

Is it supposed to be order-sensitive?

I can also make it work by adding 'autoconf 1' to the static stanza, and
omitting the auto stanza.

Richard

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#205119

Le 07/02/2019 à 10:15, Richard Hector a écrit :
>>
>> # this one should hopefully configure via SLAAC
>> iface ens3 inet6 auto
>>
>> # this one is for my static stuff (using a ULA prefix)
>> iface ens3 inet6 static
>>    address 2001:db8::1/64
>>    up ip -6 route add ...
>>    up ip -6 route add ...
>>    up ip -6 route add ...
>>
>> But I don't get the SLAAC address. The only way I've managed to get the
>> SLAAC address plus the static, is to have a single auto stanza like this:
>>
>> iface ens3 inet6 auto
>>    up ip -6 addr add 2001:db8::1/64 dev ens3
>>    up ip -6 route add ...
>>    up ip -6 route add ...
>>    up ip -6 route add ...
>>
>> Incidentally, that also gives me an autoconfigured address (based on the
>> MAC) in the 2001:db8::/64 prefix, which I don't think I need.

Huh ? Isn't it the autoconfigured address you expect to get from an 
"auto" stanza ?

>> Does that suggest a bug in ifupdown? Or am I interpreting something wrong?

I would call it more an unforeseen consequence.

> Actually, if I put the 'auto' stanza after the 'static' one, it does
> work (I still get the autogenerated address in the ULA prefix).
> 
> Is it supposed to be order-sensitive?

Yes. "auto" sets autoconf=1 to enable SLAAC, and "static" sets 
autoconf=0 by default, which disables SLAAC and removes any 
autoconfigured address.

> I can also make it work by adding 'autoconf 1' to the static stanza, and
> omitting the auto stanza.

This is the right way to go.

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#205120

Pascal Hambourg wrote: 
> Le 07/02/2019 à 10:15, Richard Hector a écrit :
> > > 
> > > # this one should hopefully configure via SLAAC
> > > iface ens3 inet6 auto
> > > 
> > > # this one is for my static stuff (using a ULA prefix)
> > > iface ens3 inet6 static
> > >    address 2001:db8::1/64
> > >    up ip -6 route add ...
> > >    up ip -6 route add ...
> > >    up ip -6 route add ...
> > > 
> > > But I don't get the SLAAC address. The only way I've managed to get the
> > > SLAAC address plus the static, is to have a single auto stanza like this:
> > > 
> > > iface ens3 inet6 auto
> > >    up ip -6 addr add 2001:db8::1/64 dev ens3
> > >    up ip -6 route add ...
> > >    up ip -6 route add ...
> > >    up ip -6 route add ...
> > > 
> > > Incidentally, that also gives me an autoconfigured address (based on the
> > > MAC) in the 2001:db8::/64 prefix, which I don't think I need.
> 
> Huh ? Isn't it the autoconfigured address you expect to get from an "auto"
> stanza ?

I bet there's at least a little confusion between

auto ens3

and

iface ens3 inet6 auto

the first one tells the system to bring ens3 up at boot time;
the second one tells the system what to do with ens3.


-dsr-

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#205123

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On 8/02/19 8:30 AM, Dan Ritter wrote:
>> Huh ? Isn't it the autoconfigured address you expect to get from an "auto"
>> stanza ?
> I bet there's at least a little confusion between
> 
> auto ens3
> 
> and
> 
> iface ens3 inet6 auto
> 
> the first one tells the system to bring ens3 up at boot time;
> the second one tells the system what to do with ens3.

In general, perhaps. Not on my part, I don't think.

Though I concede I should have included 'auto ens3' in my example.

Richard

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#205122

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On 8/02/19 8:08 AM, Pascal Hambourg wrote:
> Le 07/02/2019 à 10:15, Richard Hector a écrit :
>>>
>>> # this one should hopefully configure via SLAAC
>>> iface ens3 inet6 auto
>>>
>>> # this one is for my static stuff (using a ULA prefix)
>>> iface ens3 inet6 static
>>>    address 2001:db8::1/64
>>>    up ip -6 route add ...
>>>    up ip -6 route add ...
>>>    up ip -6 route add ...
>>>
>>> But I don't get the SLAAC address. The only way I've managed to get the
>>> SLAAC address plus the static, is to have a single auto stanza like
>>> this:
>>>
>>> iface ens3 inet6 auto
>>>    up ip -6 addr add 2001:db8::1/64 dev ens3
>>>    up ip -6 route add ...
>>>    up ip -6 route add ...
>>>    up ip -6 route add ...
>>>
>>> Incidentally, that also gives me an autoconfigured address (based on the
>>> MAC) in the 2001:db8::/64 prefix, which I don't think I need.
> 
> Huh ? Isn't it the autoconfigured address you expect to get from an
> "auto" stanza ?

Sorry for the confusion. I expected to get a autoconfigured address in
the prefix the router got from the isp, not in a ULA one I created
myself. However, it's starting to look like the router actually does
advertise the ULA as well (I thought it didn't), so that's probably
correct behaviour.

>>> Does that suggest a bug in ifupdown? Or am I interpreting something
>>> wrong?
> 
> I would call it more an unforeseen consequence.
> 
>> Actually, if I put the 'auto' stanza after the 'static' one, it does
>> work (I still get the autogenerated address in the ULA prefix).
>>
>> Is it supposed to be order-sensitive?
> 
> Yes. "auto" sets autoconf=1 to enable SLAAC, and "static" sets
> autoconf=0 by default, which disables SLAAC and removes any
> autoconfigured address.

I didn't find anywhere in the man page that said the order of my stanzas
was important - I assumed they were entirely independent of each other.

>> I can also make it work by adding 'autoconf 1' to the static stanza, and
>> omitting the auto stanza.
> 
> This is the right way to go.

And it's the way I'm going.

It just appears that the idea of using one stanza per ip address (or at
least per prefix) doesn't seem to work consistently.

Cheers,
Richard

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#205138

Le 08/02/2019 à 04:00, Richard Hector a écrit :
> 
> However, it's starting to look like the router actually does
> advertise the ULA as well (I thought it didn't)

AFAIK, a router does not advertise a prefix by itself, if it has not 
been configured to do so.

> It just appears that the idea of using one stanza per ip address (or at
> least per prefix) doesn't seem to work consistently.

It works to configure up multiple static addresses on an interface. It 
may not work as expected to configure addresses using multiple methods 
which set interface parameter values conflicting with each other.

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