Hi,
First of all, thanks for the answers!
Regarding your comments, it looks I did not made myself very clear! I
answered below.
This property of remembering mappings is what makes NAT64
"stateful". Its advantage is that you're using a few G64 addresses
to grant a potentially large and dynamic number of IPv6 nodes
access to IPv4 ones. The drawback is that IPv4 nodes cannot start
communication with v6 ones because G64 doesn't initially know who
they are talking to.
(Unless you predefine mappings yourself. You can find more
information at https://jool.mx/en/bib.html and
https://jool.mx/en/usr-flags-bib.html)
I understand the mapping concept, and this question was for when G64
already created the mapping for UDP between the IPv6 address and the
IPv4 one (when using a pool4).
This drawback is exactly why I would want some kind DHCPing to happen:
I.E. when Jool creates a mapping between one IPv6 and an IPv4 (this
would only happen on A6-initiated traffic), I would like for it to ask
to the DHCP for an address instead of randomly grabbing one from the
pool4. And this mapping would have the same TTL as the allocation from
the DHCP server.
I read the doc for the bib entries, it would be perfect, except my only
problem with those is that I would have to manually add every device as
soon as it appears on the network. And I'm not sure how to do that (yet!
Maybe I could broadcast a ping or use neighbour discovery to find IPv6
devices and attribute them a fixed entry, all from within a script that
would also push new bib commands).
One of the downsides of SIIT is that this "predetermination" of
address mappings is not going to be friendly with your "Every IPv6
device has a somewhat unpredictable IP where the prefix is
fg01::/64" requirement.
You can either find a way to impose more order to your address
assignment policies (so they will be friendlier to SIIT's
constraints)
Yes, this is why I can't use SIIT. I can't impose more constraints on
the IP of these devices...
or you can try Taiga (http://www.litech.org/tayga/).
Tayga is a SIIT/NAT64 hybrid in that it can assign v4 addresses to
IPv6 nodes on the fly, and then the entire address (not just an
address and port) are assigned to the IPv6 node. I can't vouch for
Tayga because I don't use it and hasn't received updates in a long
time, but perhaps you can squeeze something out of it.
I tried it! But it doesn't compile out of the box for kernel 4.1.15. I
didn't have time to investigate where the problem comes from.
Alternatively, you might want to open this hybrid operation mode as
a feature request for Jool: https://github.com/NICMx/Jool/issues
That's an idea! I'll try and define more precisely the expected behavior
before putting it up in Github.
> Here, I reckon that the gateway does not know that packets on the
> network with the 192.168.0.54 address are in fact destined to
> her, because when I manually add this IP to eth0 (with ip addr
> add 192.168.0.54/24 <http://192.168.0.54/24> dev eth0 ), suddenly,
it works!
A NAT64 is a device that masks IPv6 nodes behind it using its own
IPv4 address (or addresses).
An SIIT is a device that renames your IPv6 nodes, each using a
separate IPv4 address, without them realizing it.
Pay special attention to the part where I say "using its own IPv4
address". NAT64 does not rename v6 nodes like SIIT does; it
pretends it itself is the IPv6 nodes it is masking. That's why they
are called "masks" :)
So yes; the v4 nodes need to be fooled into thinking that G64 *is*
the v6 network. One way to do that is by adding the addresses to
G64's interface. (So G64 answers ARP "neighbor" requests to these
packets.)
Yes, I got that. But then, when we define a pool4, it stops doing this
when it maps an IPv6 traffic to an IPv4. Or maybe I don't understand the
use of pool4?
> How can I tell my eth0 interface that its should be concerned by
packets adressed on the 192.168.0.54 (which it used to send packets
beforehand since pinging worked), but without statically
configuring it with this IP address?
You need to realize that 192.168.0.54 belongs to C4's network
(192.168.0.54/100 <http://192.168.0.54/100>), so C4 is expecting .54
to be one of its
neighbors. For this reason, it doesn't intend to send the packet
via any gateways.
Agreed, but I think the problem comes from G64 that does not know that
indeed .54 traffic is expected to be for it (more specifically for one
of its services).
That said, you can always instead inform C4 that any traffic
towards 192.168.0.54 should be routed via G64:
romain@c4$ ip route add 192.168.0.54/32 <http://192.168.0.54/32>
via 192.168.0.100
But perhaps by this point you have realized that you should more
likely redesign the setup :p
Yes, and this is something I would like to avoid.
> Can jool automatically and dynamically requests a new IPv4 from a
DHCP server for an IPv6 device hidden behind?
No, but why would you want to do that? (maybe I'm missing
something)
I explained in the beginning of this email why I want this.
> Can jool automatically set up new address on the eth0 interface
(when they are allocated by the DHCP server)?
No, but can't a shell script do it?
It definitely could! I think Michael's proposal is quite interesting,
I'll start playing with macvlan to see how it behaves with the dhcp and
everything.
By the way: It seems that you're having trouble understanding these
concepts from the documentation. Any tips on how to improve it?
I don't yet. I think that when I have better grasp on all those things I
will be able to find areas that can be improved (if there are any).
Romain Bazile
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