Subject: RE: A use for site local addresses?

From: "Michel Py" <[email-masked]>
Date: Wed, 26 Mar 2003 15:39:34 -0800

Brian,

> Brian E Carpenter
> That's correct as long as the RFC3056 code is only enabled in
> the site border router. If it's enabled in any internal routers,
> the packets will get black holed internally.

I don't think so. They will be blackholed only if the traffic crosses a
6to4 tunnel interface, not if the 6to4 address is treated/configured as
a regular IPv6 address. If the routing table contains IGP or connected
routes with a mask of /64 as it should be the longest match route will
prevail over the 2002::/16 route associated with the tunnel interface
and traffic should flow. If there is no match in the routing table then
traffic will indeed be blackholed and that's a feature not a bug.

Michel.

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From: Pekka Savola <[email-masked]>
Date: Thu, 27 Mar 2003 09:27:31 +0200 (EET)

On Wed, 26 Mar 2003, Michel Py wrote:
> a regular IPv6 address. 

True. (But this was already stated.)

> If the routing table contains IGP or connected
> and traffic should flow. 

You're making an assumption that all nodes implementing 6to4
pseudo-intefarce take part in the IGP to get the more specific 2002:FOO
routes, or the topology is simple enough that there is only one subnet (,
and the site admin expects the default route to do the job).

I do not believe this is realistically the case for what's being proposed.

> If there is no match in the routing table then

True.

-- 
Pekka Savola                 "You each name yourselves king, yet the
Netcore Oy                    kingdom bleeds."
Systems. Networks. Security. -- George R.R. Martin: A Clash of Kings

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From: Brian E Carpenter <[email-masked]>
Date: Thu, 27 Mar 2003 17:48:27 +0100

> True. (But this was already stated.)

It's exactly what I said: RFC 3056 code is the only code that
will blackhole these packets.

> I do not believe this is realistically the case for what's being proposed.

I'm confused. When one is inside the border at which an RFC 3056 router is
placed, 6to4 addresses are exactly like any other native IPv6 address.
No host inside that border should have a 6to4 pseudo-interface.

> > traffic will indeed be blackholed and that's a feature not a bug.

True, but not specific to 6to4 addresses. Again, they are only special
in one place: a border router that has RFC 3056 switched on.

   Brian

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From: Pekka Savola <[email-masked]>
Date: Thu, 27 Mar 2003 18:57:24 +0200 (EET)

> placed, 6to4 addresses are exactly like any other native IPv6 address.

Yep.  (For nodes which don't have 6to4 pseudo-interface enabled, of 
course.)

> No host inside that border should have a 6to4 pseudo-interface.

But in reality, they do.  Some implementations even enable it
automatically.