Implementing OSPFv2

There are two ways to implement the OSPF protocol, one is done by using IP and subnet and other is done by using interfaces.
It is up to you that what you use but using it with interfaces because in later of you change your IP setting you do not need to handle the OSPF configuration again.

The following is typical network diagram which will we use to configure. The entire router will be part of area-0 and at first we will configure OSPF for R1, R2, & R3.

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OSPF Configuration via IP

This is a bit hard way because we define the networks and we need to get dive into sub-netting.  The very first step is to configure the IP addresses on interfaces and assign the process ID to an OSPF instance. In a router every process is given an ID and this is helpful during maintenance and troubleshooting. The process ID is usually set to 1 because it is the very first number and this ID could be same in all the routers. Next we need to advertise the network and pick the area of advertisement.

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router ospf 1 commands turns on the OSPF and assigns it process ID of 1.

network 192.168.0.0 0.0.0.255 area 0 defines the network and subnet mast is written is wild card manner then the area is defined.

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This is the configuration and ospf 1 tells that the protocol is OSPF and process ID is 1.

OSPF Configuration via Interface

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This is the configuration via interface notice that we do not have to create an instance we just type one command ip ospf 1 area 0 and it does all the things. This command means that turn on OSPF assign process ID 1 and put this is area-0.

There is another thing to notice which is Router ID, this is the greater IP in the router. When OSPF gets started it picks the greater IP address and assigns this is router ID. This ID is same as IP address but we can change this to something that is not an IP address. This ID is used to troubleshoot the loops. It means if I get the data with the router ID as mine it means there is a loop.
Router ID should be something identical to your router, as an example this is R2 and we can set its ID as 0.0.0.2. Notice that this IP is not routed.

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If router ID does not get changed automatically then reload the OSPF instance using process ID.

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If we want to turn on OSPF for all the networks then there is an easy way to do so.

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This opens OSPF for all networks. Now we need to make sure whether routers are sharing OSPF information or not.

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This shows router-2 is sharing information with router-2 and router-3.

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This shows router-2 is sharing information with router-1 and router-3.

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This shows router-2 is sharing information with router-1 and router-2.

OSPF Parameters

Neighbor ID is the router-ID of neighbor router.

Dead Time is the time that our router has not listened form neighbor router.

Address is the interface address of neighbor router.

Interface is the interface name of neighbor router.

State

This is the important parameter and it has many types as well. This parameter defines two things one is connection state and other is connection role. For instance, if state is Full/DR then full is connection state and DR is connection role.

Connection State

Down is the very first state where router starts OSPF and list downs the neighbor routers.

Init. Is the state where router receives the OSPF hello messages and start the initialization process.  This process checks for certain parameters in order to be able to talk to neighbor router. It checks for network address, dead timer, area number, password, and there are other underlying parameters that have to match in order to talk and start becoming neighbor. If any of the parameter does not match the router then cannot talk.

2-way is the process right after initialization process. The router says that yes we have passed the check list we are comfortable with each other let’s see whether we have anything to share and bi-directional routing as well.

ExStart is the next state where routers say yes we have routes to be exchanged and one of us has to be master to exchange routes and synchronization of database as well.

Exchange is the next state where the routers start the routes exchanging with each other.

FULL is the final state where routers have setup their databases and works together to transfer traffic.

This all process is done very quickly within seconds so you probably not going to catch other states excluding FULL.

Connection Role

This is another parameter attached with connection state. It has three modes.

/ – is the state of point-to-point connection.

DR stands for designated router, it is the router that is in charge in other words it is the primary router to handle traffic.

BDR stands for backup designated router, it is second router meaning that it is the backup router when the primary (DR) router fails it will stand up and will be in charge.

DROTHER stands for designated router other, it is every other router in the topology.

The connection-role is DR, BDR, and DROTHER when there is a multi-access network and if you know that the link between two routers is point to point then you can go to the interface and set the interface to point-to-point, but this needs to be done on both sides of link otherwise it will not work properly.

Following is the command to set point-to-point connection.

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There you can see the connection roles. If a router does not have BDR connection role in its table it means the router itself is BDR.

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This is currently network diagram.

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Prerequisites for 200-301

200-301 is a single exam, consisting of about 120 questions. It covers a wide range of topics, such as routing and switching, security, wireless networking, and even some programming concepts. As with other Cisco certifications, you can take it at any of the Pearson VUE certification centers.

The recommended training program that can be taken at a Cisco academy is called Implementing and Administering Cisco Solutions (CCNA). The successful completion of a training course will get you a training badge.

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