Subject: RE: A few comments on Site-Local Useage

From: "Michel Py" <[email-masked]>
Date: Tue, 5 Nov 2002 17:23:36 -0800

Bob,

> Bob Hinden wrote:
> Another router issue that gets talked around is should
> packets with site-local destination be forwarded to
> "default".  Given that site-local addresses are not
> created without being configured, one approach could be
> to have a "black hole" route for FEC0::/10 preconfigured
> in all routers.

There is some potential in this.

Rationale: ambiguity is a fail-safe for routes that leak in the DFZ even
though they were not supposed to and for ISPs that don't filter them
even though they were supposed to.

If we could add to this black hole a preconfigured prefix-list for each
peer that would deny FEC0::/10 ge 10 (1) that would likely be good
enough to let ambiguity go and we would make a step towards globally
unique site-locals.

(1) I am thinking about something like the default deny at the end,
except that it would be at the beginning and would be effective even
though there is no prefix-list applied to the peer. Something that would
require a separate command and a confirmation to de-activate. Why would
one want site-locals in BGP anyway?

Michel.

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From: Bill Manning <[email-masked]>
Date: Tue, 5 Nov 2002 18:02:28 -0800 (PST)

% Bob,
% 
% > Bob Hinden wrote:
% > Another router issue that gets talked around is should
% > packets with site-local destination be forwarded to
% > "default".  Given that site-local addresses are not
% > created without being configured, one approach could be
% > to have a "black hole" route for FEC0::/10 preconfigured
% > in all routers.
% 
% There is some potential in this.
% 
% Rationale: ambiguity is a fail-safe for routes that leak in the DFZ even
% though they were not supposed to and for ISPs that don't filter them
% even though they were supposed to.
% 
% If we could add to this black hole a preconfigured prefix-list for each
% peer that would deny FEC0::/10 ge 10 (1) that would likely be good
% enough to let ambiguity go and we would make a step towards globally
% unique site-locals.
% 
% (1) I am thinking about something like the default deny at the end,
% except that it would be at the beginning and would be effective even
% though there is no prefix-list applied to the peer. Something that would
% require a separate command and a confirmation to de-activate. Why would
% one want site-locals in BGP anyway?
% 
% Michel.
% 

	per interface or per-peer? (will require a better understanding
	of default behaviour of routing protocols)

	if per-peer, which routing protocol?

-- 
--bill

---

From: Pekka Savola <[email-masked]>
Date: Wed, 6 Nov 2002 08:48:56 +0200 (EET)

That still does not solve the issue of site-local being used as a source 
address.

-- 
Pekka Savola                 "Tell me of difficulties surmounted,
Netcore Oy                   not those you stumble over and fall"
Systems. Networks. Security.  -- Robert Jordan: A Crown of Swords

---

From: Mark Smith <[email-masked]>
Date: 06 Nov 2002 19:11:26 +1100

> one want site-locals in BGP anyway?

Could it be argued that if there was a need for confederations in BGP to
handle iBGP scaling, then there would a reason for site-locals to be
carried by BGP, presuming a single instance of site-local addressing
across the organisation ?