OSPF States

Operation	State	Description
Establish neighbor adjacencies	1. Down state	Negotiate master / slave relationship and DBD packet sequence number. The master initiates the DBD packet exchange.
	2. Init state	Hello packets are received from the neighbor. They contain the sending router’s Router ID. Transition to Two-Way state.
	3. Two-Way state	On Ethernet links, elect a DR, and a BDR. Transition to ExStart state.
Synchronize OSPF Databases	4. ExStart state	Negotiate master / slave relationship and DBD packet sequence number. The master initiates the DBD packet exchange.
	5. Exchange state	Routers exchange DBD packets. If additional router information is required then transition to Loading; otherwise, transition to Full.
	6. Loading state	LSRs and LSUs are used to gain additional route information. Routes are processed using the SPF algorithm. Transition to the Full state.
	7. Full state	Routers have converged.

Differences between OSPFv2 vs OSPFv3

	OSPFv2	OSPFv3
Advertises	IPv4 networks	IPv6 prefixes
Source address	IPv4 source address	IPv6 link-local address
Destination address	neighbor IPv4 unicast address 224.0.0.5 all-OSPF-routers multicast address 244.0.0.6 DR/BDR multicats address	neighbor IPv6 link-local address FF02::5 all-OSPFv3-routers multicast address FF02::6 DR/BDR multicast address
Advertise networks	`network` router command	`ipv6 ospf process-id area area-id` interface configuration command
IP unicast routing	Enabled by default	`ipv6 unicast-routing` global configuration command
Authentication	plaintext authentication or MD5 authentication	IPv6 authentication