[v6ops] Re: 464XLAT in Multi-interface environments (was: I-D Action: draft-ietf-v6ops-claton-02.txt)

[Jen Linkova <[e-mail]>]

Hi Philipp,

On Thu, Oct 31, 2024 at 2:40 AM Philipp Tiesel <[e-mail]> wrote:
> While reading draft-ietf-v6ops-claton-02, I spottet a little inconsistency that may need to some wider discussion:
>
> > 5. Enabling CLAT
> >
> > For performance and security reasons CLAT MUST NOT be enabled if the
> > node has IPv4 native connectivity over the given interface.
> > Therefore recommendations provided in this section are only
> > applicable to an IPv6-only node (a node which does not have a native
> > IPv4 default route configured).
>
> There is a subtile difference between
> - a node that has no native IPv4 on a given interface and
> - a node that has no a native IPv4 default route
>
> Let’s consider the following case: I have a node with a 3GPP interface that has a native IPv4 address and no IPv6, e.g., because of data roaming, and a Wifi interface that has no IPv4 address and can be configured for 464XLAT with a NAT64 prefix discovered by PRE64 RA option.
>
> The former definition (no native IPv4 on a given interface) would allow the OS to use 464XLAT on the (most probably preferable) Wifi interface while the latter (no a native IPv4 default route on the node) would not.
>
> I would suggest either to remove the second sentence from section 5 or add some more detailed discussion on this case (happy to contribute text if requested).

Ah, yes, good catch, thank you!
Originally we defined 'IPv6-only node' as a node w/o non-link-local
IPv4 address on a given interface. However, as a result of the most
recent discussion in -02 we changed it to 'no default route' , as it
might be easier to check.
We need to replace "a native IPv4 default route" with "a native IPv4
default route pointing to that interface" - indeed, any IPv4 default
route configured on another interface shouldn't impact the clat
instance.

-- 
Cheers, Jen Linkova