From: Anthony Kirkham [mailto:[email protected]]
Sent: Tuesday, October 04, 2011 8:24 PM
To: George, Wes; [email protected]
Subject: Re: [GROW] Final feedback please - kirkham-private-ip-sp-cores

George,

I have not included discuss of implications for an IS-IS hidden core. I agree 
with your comments, however, I thought that discussion was moving a little away 
from the core topic.

well...
I was making the suggestion based on the following text from the draft:
A second approach to preventing external access to the core is IS-IS
   core hiding.  This technique makes use of a fundamental property of
   the IS-IS protocol which allows link addresses to be removed from the
   routing table while still allowing loopback addresses to be resolved
   as next hops for BGP.  The technique prevents parties outside the AS
   from being able to route to infrastructure addresses, while still
   allowing traceroutes to operate successfully.  IS-IS core hiding does
   not have the same practical requirement for the core to be addressed
   from a small number of contiguous address blocks as with iACLs.

I realize that you're suggesting it as an alternative to using 1918 space as a 
means to protect the core links, but it has some of the same problems. If you 
don't plan to discuss at least the commonalities of the problems between the 
two options because it moves away from the core topic, then I would remove this 
paragraph altogether. Otherwise, I think you can get away with adding a line or 
two regarding the limitations of "...while still allowing traceroutes to 
operate successfully..." Possibly something as simple as "but care must be 
taken to ensure that traceroutes are using source and destination addresses 
that all of the routers on the path have in their routing table."

Thanks
Wes

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