CCNP (642-902) OSPF Simulation

OSPF is configured on routers Indianapolis and Atlanta. Indianapolis’s S0/0 Interface and Atlanta's S0/1 interface are in Area 0. Atlanta’s Loopback0 interface is in Area 2.



You task is to configure the following:

• Portland’s S0/0 interface in Area 1
• Indianapolis’s S0/1 interface in Area 1
• Use the appropriate mask such that ONLY Portland’s S0/0 and Indianapolis’s S0/1 could be in Area 1.
• Area 1 should not receive any external or inter-area routes (except the default route).

To download this lab : https://app.box.com/s/izbu1wcbjxdz32hsa1gx

Answer:

Portland Configuration:

Task 1: Portland’s S0/0 interface in Area 1
Task 3: Use the appropriate mask such that ONLY Portland’s S0/0 and Indianapolis’s S0/1 could be in Area 1.


The Portland’s S0/0 IP Address is 192.168.4.5/30. So, we need to find the network address and wildcard mask of 192.168.4.5/30 in order to configure the OSPF.

IP Address : 192.168.4.5 /30
Subnet Mask : 255.255.255.252

Here subtract 252 from 2565, 256-252 = 4, hence the subnets will 4 increment. Like 0, 4, 8, 12, ...

Lets find the 4th octet of Network Address:

Subnet	Network	Broadcast
0	0	3
1	4	7
2	8	11
3	12	15
4	16	19
5	...	...

The 4th octet of IP address (192.168.4.5) belongs to subnet 1 ( 4 to 7).

Network Address : 192.168.4.4
Broadcast Address : 192.168.4.7



Lets find the wildcard mask of /30.

Subnet Mask : (Network Bits – 1’s, Host Bits – 0’s)

/30	11111111	11111111	11111111	11111100
	255	255	255	252

Wildcard Mask : (Network Bits – 0’s, Host Bits – 1’s)

/30	00000000	00000000	00000000	00000011
	0	0	0	3

First check your OSPF Process Number by using the command:

Portland>enable
Portland#show run
<output omitted>
!
router ospf 1
!

Portland>enable
Password:
Portland#conf t
Portland(config)#router ospf 1

Portland(config-router)#network 192.168.4.4 0.0.0.3 area 1

Task 4: Area 1 should not receive any external or inter-area routes (except the default route).

Portland(config-router)#area 1 stub
Portland(config-router)#end
Portland#copy run start

Indianapolis Configuration:

Indianapolis>enable
Password: cisco
Indianapolis#conf t
Indianapolis(config)#router ospf 1

Task 2: Indianapolis’s S0/1 interface in Area 1

Indianapolis(config-router)#network 192.168.4.4 0.0.0.3 area 1

Task 4: Area 1 should not receive any external or inter-area routes (except the default route).
In order to accomplish Task 4, we must stop LSA Type 5 if we don’t want to send external routes. And if we don’t want to send inter-area routes, we have to stop LSA Type 3 and Type 4. Therefore we have to configure area 1 as a totally stubby area.

Indianapolis(config-router)#area 1 stub no-summary

Indianapolis(config-router)#end
Indianapolis#copy run start