Re: NAT64 in RA, draft-ietf-6man-ra-pref64

[David Farmer <[e-mail]>]

On Tue, Jul 2, 2019 at 8:11 AM Jen Linkova <[e-mail]> wrote:

> On Tue, Jul 2, 2019 at 10:09 PM David Farmer <[e-mail]> wrote:
> > I mostly agree, but there is a scenario I've been thinking about;
> >
> > What if the network operator doesn't want RFC1918 and RFC 6598 IPv4
> addresses synthesized at all? I suppose the NAT64 function could block
> these addresses. However, for a large enough population that could be a lot
> of useless traffic going to the NAT64 function. While on the other hand
> some network operators, especially enterprise operators, will probably want
> these addresses synthesized.
>
> Oh funny you should mention that..I've been thinking about it but have
> not managed to untangle the chain of RFCs yet...
>

Actually, I was rereading the draft and found a possible answer for my
scenario already partially discussed in the draft.

Section 4, paragraph 2, says;

   This option specifies exactly one NAT64 prefix for all IPv4
   destinations.  If the network operator desires to route different
   parts of the IPv4 address space to different NAT64 devices, this can
   be accomplished by routing more specifics of the NAT64 prefix to
   those devices.  For example, if the operator would like to route
   10.0.0.0/8 through NAT64 device A and the rest of the IPv4 space
   through NAT64 device B, and the operator's NAT64 prefix is
   2001:db8:a:b::/96, then the operator can route
   2001:db8:a:b::a00:0/104 to NAT64 A and 2001:db8:a:b::/64 to NAT64 B.

One answer for my scenario is if the NAT64 prefix is 2001:db8:a:b::/96,
then null route or filter traffic for 2001:db8:a:b::a00:0/104 and the other
RFC1918 blocks in the network ahead of the NAT64 function, then it won't
see the traffic.

Maybe add something about filtering or null routing as well as routing to
an alternate NAT64 function to the above paragraph.

Thanks.

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