In the previous video, we already create topology with 2 router, now in this video we are going to 2
configure ospf in this topology. The concept of ospf is same as eigrp, which is each router must 3
advertise their connected network. So for example here router 1 must be have 2 connected network, 4
which is 10.10.10.0/24 connected to fa0/0, and 192.168.1.0/24 connected to fa0/1. 5
Router 2 must be have 2 connected network, 6
10.10.10.0/24 connected to fa0/0 and 192.168.2.0/24 connected to fa0/1. 7
So router 1 and router 2 must advertise 2 network. 8
Let’s start configuring router 1, the command is router ospf, if we use eigrp, 9
we must define autonomous system number, but in ospf, we must define ospf process id. 10
Here let’s exit first. 11
And then router ospf and question mark, here we can see that we need to define ospf process id. 12
In the eigrp, the autonomous system number must be same on all routers, but in ospf, 13
because this is only ospf process id, so the number can be different in each router. 14
Let’s say in router 1, we use router ospf 1, in router 2 we use router ospf 2, 15
and in router 3 we use router ospf 3, this is will work. 16
Or if we use same ospf process id in all router, this is also work. 17
Okay, let’s say here we use 1, 18
Next we need to advertise all of connected network. Let’s advertise 10.10.10.0/24, 19
so network 10.10.10.0, in the eigrp, the command is just like this and we can enter, but in ospf, 20
we need to add some argument, question mark, 21
Here we need to define wildcard bits, 22
what is wildcard bits? Wildcard bits is the reverse of subnetmask. 23
We know that for prefix /24, the subnetmask is 255.255.255.0. 24
And then, to calculate wildcard bits, the formula is 255.255.255.255 minus by subnetmask. 25
In this case, the prefix is /24, and the subnetmask for prefix /24 is 255.255.255.0. 26
So here 255 minus by 0 is 255, 255 minus by 255 is 0, 27
255 minus by 255 is 0 and 255 minus by 255 again is also 0. 28
So the wildcard bits for prefix /24 is 0.0.0.255 29
Okay, this is how we calculate wildcard bits. 30
Now let’s back to the configuration, 31
so here the wildcard bits is 0.0.0.255. And then question mark again, here we need to define area, 32
and then question mark, we must define the area number. For now, let’s just use area 0. 33
Okay now we have done advertise network 10.10.10.0. 34
Next, let’s advertise the network that connected to pc 1. 35
So here, network 192.168.1.0 0.0.0.255 area 0. 36
Okay now we have done configuring ospf on router 1, next let’s configure on router 2. 37
Enable, configure terminal, and then router ospf, remember that 38
here we need to define ospf process id, and ospf process id doesn’t have to be same. 39
In the router 1 we use process id 1, let’s say here we will use process id 2. 40
Next, let’s advertise the network, network 10.10.10.0 0.0.0.255 area 0. 41
Next let’s advertise the network that connected to pc 2, so network 192.168.2.0 0.0.0.255 area 0. 42
Okay now we have done configuring ospf on router 1 and router 2. 43
Let’s verify it, do show ip ospf neighbor, here we can see that now we have ospf neighbor, 44
and the status is full. This is means that the ospf is UP. 45
Let’s also check the routing table, do show ip route, here we can see that from router 2, 46
we have route to 192.168.1.0/24, the label is O, this is means ospf. 47
Let’s also check on router 1, do show ip route, 48
here we can see that router 1 also have a route to 192.168.2.0/24 and the label is o. 49
So now pc 1 and pc 2 should be able to communicate each others. Let’s try, failed, let’s test again, 50
and here success. 51
Okay so now we have done configuring dynamic routing ospf. 52
I think enough for this video, in the next video, we are going to add 1 more router to our topology. 53
Thank you for watching and see you on the next video.