[c-nsp] Late night BGP puzzler

[Euan Galloway]

On Thu, Aug 02, 2007 at 08:38:36AM -0700, Peter Kranz wrote:
> Unfortunately, MED comes too late in the process for this example (equal as
> path length routes from 2 different AS#, one IGP and one EGP).

The "Origin" (step 5) of both was "IGP".

  2914 701 668
    128.241.219.33 from 128.241.219.33 (129.250.0.39)
      Origin IGP, metric 11, localpref 10, valid, external, best
      Community: 2914:420 2914:2000 2914:3000 32354:300
      Extended Community: Cost:igp:1:10
  174 701 668
    204.11.106.1 (metric 11) from 204.11.106.1 (204.11.106.1)
      Origin IGP, metric 0, localpref 10, valid, internal
      Community: 174:21000 174:22013 32354:300
      Extended Community: Cost:igp:1:8

The difference was at step 7 "Prefer eBGP over iBGP paths."

Which thankfully comes before step 6 "Prefer the path with the lowest multi-exit discriminator (MED)." (huge list of med related caveats apply).

Unless we changed example at some point and I lost track...

-- 
Euan Galloway