Authentication

OSPFv2 authentication is performed in two steps:
        * Enable OSPF authentication (per interface, or per area).
        * Configure the authentication key, per interface.

Authentication Type
        * 0 (No authentication)
        * 1 (Simple password authentication)
        * 2 (Cryptographic authentication)

Authentication Method
OSPF support two authentication methods
        * Plane text
        * MD5

Interface Based Authentication

Commands
                 interface fastEthernet0/0
                 ip ospf authentication message-digest
                 ip ospf message-digest key 1 md5 ccie

Process Based Authentication

Commands
                router ospf 1
                 area 1 authentication message-digest

we can apply only authentication in process based, we can't define key in process based authentication

Default-Route Origination

1. default-information originate
        a. if a default route is present in routing table
        b. OSPF router generates default route in LSA-5 database
2. default-information originate always
        a. no need to have default route in routing table
        b. OSPF router generates default route in LSA-5 database
3. default-information originate route-map_____
        a. conditional default route using ACL
        b. OSPF router generates default route in LSA-5 database
4. Area 10 stub
        a. While using the concept of Stub area
        b. ABR generates a default route in LSA-3 Database

Default Route Cost

        * By default, the stub ABR advertises a default route with cost equal to 1
        * Cost can be changed using the area area-id default-cost command
        * Useful for primary/backup setup with multiple exit points
By default, the ABR of a stub area will advertise a default route with a cost of 1. You can change the cost of the default route by using the area default-cost command. The default-cost option provides the metric for the summary default route that is generated by the ABR into the stub area.