Ripe 181

  > bmanning at ISI.EDU writes:
  > Well, this is perhaps incorrect. I should perhaps state that local preferen
  > ce
  > should be cast inside global preference. In this case, if I am delegated
  > a /27 mask from a larger /24 mask, I ought to be able to override the
  > preferences of the /24 registration. Something along the lines of BGPs 
  > longest match. In the absence of the more specific (local) preference,
  > use the more generic (global) preference.
  > 
  > Does this make sense?

It does.

But it is not relevant for the local/global discussion at hand.
This does not concern "specificness" of routes as in "longest match".
It concerns local variations of policy (across peerings to the same
neighbor) over the global policy (between different neighbors).

------------

You raise an interesting point iabout counter intuitive behaviour
of CIDR though: 

AS1 is connected to AS2 and AS3

AS1 policy says to prefer all routes learned from AS2 over anything
learned from AS3

AS3 announces a more specific route inside a route announced by AS2.

According to CIDR rules the more specific route takes precedence.
My gut says that some properties of BGP-4/IDRIP may actually depend on this.

Those specifying the routing policy would probably want less specific route 
to take precedence because they do not trust AS3 as much.

-------------

For RIPE-181 this is a non issue, since it describes preferences between
exactly equal routes (length *and* prefix) only. 

Daniel



-------- Logged at  Thu Oct 13 18:15:13 MET 1994  ---------