[j-nsp] What in deity's name does export-rib do and will I ever need it?

Sebastian Wiesinger juniper-nsp at ml.karotte.org
Wed Mar 4 09:05:43 EST 2015


Hello,

I'm just doing some lab experiments with rib-groups and importing BGP
routes from inet.0 into VRFs. Ever so often export-rib shows up in
discussions/documentation. I wanted to read about this elusive config
option and now I'm about to throw the towel and just ignore it.

I think I now read about 4-5 opinions/statements about what export-rib
does, from "it doesn't work at all" to "you need it or you'll loose
your BGP routes in inet.0".

There is Juniper KB16133 that states:

  The export-rib command tells the router, from which tables to take
  information. For any individual RIB group, only one table can be
  specified in the export-rib statement.

And then there is this Juniper forum entry:
http://forums.juniper.net/t5/Routing/import-rib-VS-export-rib-in-RIB-group-Configuration/td-p/94202

  Regarding a popular assumption of "first table is source and second
  is destination" - I think this comes from "routing-options
  interface-routes" stanza where one usually specifies inet.0 as
  1st/primary table and VRF/VR tables as 2nd/3rd/4th etc.And because
  all interface routes are always in inet.0, this creates assumption
  that interface-routes are exported from inet.0 to VR/VRF tables.
  This is a fair assumption since one cannot filter interface-routes
  on their way to inet.0 (to prevent shooting self in the foot :-) but
  the actual import is "from protocol" and "into primary
  table+secondary tables".

So while I try this out in the lab, could someone tell me what exactly
the purpose of this option is and if I need it at all?


Regards

Sebastian

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