[Cerowrt-devel] CeroWrt port numbering

Dave Taht dave.taht at gmail.com
Fri Mar 2 10:56:08 EST 2012

On Fri, Mar 2, 2012 at 7:37 AM, Richard Brown
<richard.e.brown at dartware.com> wrote:

> I don't (yet) have facilities for testing IPv6 here, so I can't offer any advice

I'm going to get to where I have a ula generating script to make that
easier. soon. (unfinished draft  in ceropackages/ipv6/ipv6policy)

>>> - I'm a little surprised that the babel interfaces both have ...224/32. (But I don't know anything about babel...)
>> Actually that's an 'AHCP'-ism. Babel is capable of mesh routing, and
>> with p2p wireless links nothing more than a /32 or /128 (for ipv6) is
>> needed to be distributed on mesh node links.
>> It makes failover simpler in the mesh routing case.
> I was just curious whether they were meant to be the same /32 address...

yes. The routing scheme figures out the right interface with using the
/32 or a /128 on the same ip.


I'd been doing mesh networking for a long time prior
to this project. I still find it kind of wierd to disconnect
from my wired interface and go wireless and lose all
my ssh connections. Others seem to find this normal,
but it makes me mildly nuts.

with a full mesh config, which is not the default cero can
fails over to wireless in a split second,
moves back to wired in a few seconds when you plug in the wired
connection, no connection loss, no muss no fuss.

>>> - I'm confused about the OUI's for the interfaces. As expected, C4:3D:C7... is the OUI for Netgear. But C6:3D:C7... isn't allocated to anyone. Is that by design?
>> Two issues:
>> There is no separate mac address for one of the network devices on the
>> wndr, so we take a known good address from one of the devices, and
>> flip the 'local mac' bit.
> Ahah. I learn something every day. The 0x02 bit of the most significant byte is the "local" bit; the 0x01 bit is the multicast bit. See:  http://en.wikipedia.org/wiki/Organizationally_Unique_Identifier
>> Each wireless VIF creates it's own mac address as well, based on
>> incrementing the underlying mac, and I don't remember the algo
>> offhand.
> Yes, that makes sense. But...
> I still don't understand the reasoning behind the mix and match (see list below). Why wouldn't you put all the wireless together as C4:... and Ethernet on the other? Or divide by 2.4GHz or 5GHz? or Secure vs. Guest, or some other scheme? (Or is it purposely to prevent people like me from imputing meaning where none is needed? :-)

I think your diagnosis is correct.

>>> - I don't understand the pattern of the OUIs for the interfaces: why is the C4 prefix issued to the Ethernet ge00 and wireless sw00 and sw10, while C6 goes to Ethernet se00 and the remaining wireless interfaces?
>>> - I also note that the MAC addresses sort to an odd order, intermixing ethernet and wireless. (This is related to the previous item.)
>>> sw00    C4:3D:C7:9D:E3:9A
>>> ge00    C4:3D:C7:9D:E3:9B
>>> sw10    C4:3D:C7:9D:E3:9C
>>> se00    C6:3D:C7:9D:E3:9A
>>> gw00    C6:3D:C7:9D:E3:9B
>>> gw01    C6:3D:C7:9D:E3:9C
>>> gw10    C6:3D:C7:9D:E3:9D
>>> gw11    C6:3D:C7:9D:E3:9E
>> Hopefully what I wrote above sort of explains this.
>>> - Finally, I haven't fired up 6to4 or anything, but will the global IP address assignments be randomized more than the local (fe80) address?
>> Not sure what you mean here.
> Privacy advocates are saying that the "easy way" to create a global IPv6 address is bad: it's too easy to plop the MAC address in the lower 64 bits of your address, and then the bad guys can use that as another (really powerful) tracking identifier. This is clearly not a CeroWrt-specific issue, and it's actively in discussion. (See, for example Barrera et al, in the Usenix Vol 36, Number 1, https://www.usenix.org/system/files/login/articles/105438-Barrera.pdf )

This debate has been going on for a decade.

I would like all those trying to make ipv6 even harder for mere
mortals to use to go off and work on ipv7, hip, and the like.

DNS naming has been hopelessly screwed up as it is, and while I'm a
big privacy advocate, I'd like ip addresses to be mapped to DNS names
and I figure that that will bug that crowd, too.

See also 'dname debacle'


> Thanks!
> Rich

Dave Täht
SKYPE: davetaht
US Tel: 1-239-829-5608

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