OSPF Overview
The OSPF (Open Shortest Path First version 2) protocol is an interior gateway protocol (IGP) that routes packets within a single autonomous system (AS). OSPF uses link-state information to make routing decisions.
The OSPFv3 (Open Shortest Path First version 3) protocol is configured the same way as OSPFv2, except with the following differences:
- OSPFv3 propagates Internet Protocol Version 6 (IPv6) packets, while OSPFv2 propagates Internet Protocol Version 4 (IPv4) packets.
- Authentication is removed for OSPFv3. IPv6 uses IPSec for authentication.
- OSPFv3 does not support point-to-multipoint (P2MP)
- OSPFv3 does not support routing instances.
The term OSPF refers to both OSPFv2 and OSPFv3.
This chapter discusses the following topics that provide background information about OSPF: