OSPF Path selection

RFC 1587 states that OSPF used the following path selection order when choosing a path:

  • Intra-Area (O)
  • Inter-Area (O IA)
  • External Type 1 (E1)
  • NSSA Type 1 (N1)
  • External Type 2 (E2)
  • NSSA Type 2 (N2)

RFC 3101 has since revised this order to:

  • Intra-Area (O)
  • Inter-Area (O IA)
  • NSSA Type 1 (N1)
  • External Type 1 (E1)
  • NSSA Type 2 (N2)
  • External Type 2 (E2)

Cisco IOS version 15.1(2)S and later adheres to the RFC3101 order while earlier versions adhere to the RFC1587 order

Links:

https://networklessons.com/ospf/ospf-path-selection-explained/

https://tools.ietf.org/html/rfc1587

https://tools.ietf.org/html/rfc3101

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