[c-nsp] Rationale for ISIS default origination behavior

[Gert Doering]

Hi,

On Tue, Jan 22, 2013 at 07:47:59PM +0200, Saku Ytti wrote:
> On (2013-01-22 17:50 +0100), Gert Doering wrote:
> 
> > I'm still not convinced that this is more elegant than "the to-upstream
> > edge routers just inject a static default route (pointing to the upstream
> > peer) into IGP".  What's the benefit of the extra recursion?
> 
> If you point it at peer IP, it'll be valid route, as long as peer interface
> is UP. This does not mean it's usable egress.
> 
> If at edge you point it to some 8.8.8.8 without interface and send
> next-hop-self, it'll advertise it, even if local edge is down as it'll
> recurse to any available edge presuming edge has full table.

And if 8.8.8.8 should ever disappear from the table for whatever reason
(even Google might have an outage), your default route disappears - I'm 
not sure I consider *that* a very good idea.

[..]
> And if it works in your platform and you can choose option with same
> results, where one gives you default free BGP and one does not, for me,
> choice is easy.

No need to put the default route into BGP.  I wrote IGP above :-)

gert
-- 
USENET is *not* the non-clickable part of WWW!
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Gert Doering - Munich, Germany                             gert at greenie.muc.de
fax: +49-89-35655025                        gert at net.informatik.tu-muenchen.de
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