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OSPF (7 states to become neighbors (Down - no OSPF neighbors detected at…

- - - - Each OSPF router needs to have an unique ID which is the highest IP address on any active interface. If you have a loopback interface on your OSPF router then this IP address will be used as the router ID even when it’s not the highest active IP address.
    - - Every X seconds we are going to send a hello packet, if we don’t hear any hello packets from our network for X seconds we declare you “dead” and we are no longer neighbors.
    - - All other routers who are your neighbors are specified in the hello
        packet.
    - - This is the area you are in. This value has to match on both sides in order to become neighbors.
    - - This value is used to determine who will become designated or
        backup designated router.
    - - Designated router
    - - Backup Designated router
    - - You can use clear text and MD5 authentication for OSPF which means every packet will be authenticated. Obviously you need the same password on both routers in order to make things work
    - - Both routers have to agree on the area type in order to become neighbors.
- - - - Process of Election
        
        Caracteristics
        
        The router with the highest priority will become DR.
        
         The router with the second highest priority will become BDR.
        
         If the priority is the same the OSPF router ID is the tiebreaker.
        
        You change the priority if you like by using the ip ospf priority command
        
        The default priority is 1.
        
         A priority of 0 means you will never be elected as DR or BDR.
        
         You need to use clear ip ospf process before this change takes effect
        
         The higher router ID the better.
        
         DR/BDR election is non-preemptive. This means if you change the priority or router
        
        ID you have to reset OSPF in order to select a new DR/BDR.
        
         Routers that are not DR or BDR show up as DROTHER