Things to remember on Redistribution

 Below are some key points to remember on Redistribution.

  • When redistributing from OSPF in to BGP, by default, BGP only accepts internal routes not external type-1 or type-2. Also, the routes learnt via iBGP will not be redistributed into OSPF with the use of "redistribute" command until "bgp redistribute-internal" is used under bgp process.
  • When redistributing into OSPF all redistributed routes get a metric of 20, except BGP gets a metric of 1.
  • EIGRP needs a default-metric command or a metric when redistributing with route-map or with the redistribute metric xxx command.
  • Watch for RIP metrics set to redistributed routes, might end up with 16, use metric, again in route-map or redistribute metric command.
  • Only IS-IS Level-2 routes are redistributed by default
  • Watch for administrative distance problems, especially since EIGRP has lower distance than OSPF.
  • Beware of the metric used by RIP
  • Redistributing in to RIP requires a metric or default-metric or it may get set to 16.
  • Always filter routes when doing redistribution the use of route TAGS is extremely useful and sometimes necessary (to conserve time and headaches).
  • BGP only redistributes eBGP routes by default (bgp redistribute internal) to change that.
  • Make note of routes in routing table and from which protocol. Only routes in routing table get redistributed.
  • Always watch for multiple points of redistribution and routes from a higher AD protocol going into a lower AD protocol then back into Higher AD, use route TAGS as well for this.

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