Erik Nordmark wrote:
Correct.  My statement was for the protocol, not the forwarding.
That is why I made the follow-on comment about complexity.  The
next-hop interface's ifindex for the global destination address
would have to be checked to ensure that it has the same zone ID
as the interface on which the packet was received.  So, it leads
to more checks during forwarding AND requires the forwarding table
to potentially maintain multiple next-hops for the global addresses.


I don't think that is sufficient.
If all the entries in the RIB for the prefix point outside the site
then you have no choice but to drop the packet on the floor.

If the sender had used a global source the packet would have made it
through.

Yes. I agree that would happen. That is why it has an operational component as well. Lets say we have something like this:

        +------------ Internet -------------+
        |                                   |
     office1 ------ site local / ------- office2
                      global

A node in office1 could communicate with a node in office2 using
any combination of SLs and Globals (per the existing specs) as long
as both offices were in the same site.  Using your example of
global dest and SL src, everything is fine until the internal link
breaks.  Now, the source node would get back a "scope exceeded"
ICMP message when the router tries to send the packet over the
Internet.  So now the source picks a global src to go with the GL
dest.  The packet may get through unless the routers or firewalls
drop it when they realize that the destination is really inside
but isn't reachable.  If it does get through, then the source may
have sent sensitive information over the Internet without encrypting
it.

What I am saying is that the routing and forwarding can be made to
work, but it is kludgy and a big impact on performance.

Brian

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