Lab Simulation 1

Lab Simulation 1 – OSPF
Route.com is a small IT corporation that is attempting to implement the network shown in the exhibit. Currently the implementation is partially completed. OSPF has been configured on routers Chicago and NewYork. The S0/0 interface on Chicago and the S0/1 interface on NewYork are in Area 0. The loopback0 interface on NewYork is in Area 1.
However, they cannot ping from the serial interface of the Seattle router to the loopback interface of the NewYork router.
You have been asked to complete the implementation to allow this ping.
ROUTE.com’s corporate implementation guidelines require:
– The OSPF process ID for all routers must be 10.
– The routing protocol for each interface must be enabled under the routing process.
– The routing protocol must be enabled for each interface using the most specific wildcard mask possible.
– The serial link between Seattle and Chicago must be in OSPF area 21.
– OSPF area 21 must not receive any inter-area or external routes.
Network Information
Seattle
S0/0 192.168.16.5/30 – Link between Seattle and Chicago
Secret Password: cisco
Chicago
S0/0 192.168.54.9/30 – Link between Chicago and NewYork
S0/1 192.168.16.6/30 – Link between Seattle and Chicago Secre
Password: cisco
NewYork
S0/1 192.168.54.10/30 – Link between Chicago and NewYork
Loopback0 172.16.189.189
Secret Password: cisco

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Answer:
Note: In actual exam, the IP addressing, OSPF areas and process ID, and router hostnames may change, but the overall solution is the same.
Seattle’s S0/0 IP Address is 192.168.16.5/30. So, we need to find the network address and wildcard mask of 192.168.16.5/30 in order to configure the OSPF.
IP Address: 192.168.16.5 /30
Subnet Mask: 255.255.255.252
Here subtract 252 from 2565, 256-252 = 4, hence the subnets will increment by 4.
First, find the 4th octet of the Network Address:

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The 4th octet of IP address (192.168.16.5) belongs to subnet 1 (4 to 7).
Network Address: 192.168.16.4
Broadcast Address: 192.168.16.7
Lets find the wildcard mask of /30.
Subnet Mask: (Network Bits 1’s, Host Bits 0’s)
Lets find the wildcard mask of /30.

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Now we configure OSPF using process ID 10 (note the process ID may change to something else in real exam).
Seattle> enable
Password:
Seattle# conf t
Seattle(config)# router ospf 10
Seattle(config-router)# network 192.168.16.4 0.0.0.3 area 21
One of the tasks states that area 21 should not receive any external or inter-area routes (except the default route).
Seattle(config-router)# area 21 stub
Seattle(config-router)# end
Seattle# copy run start
Chicago Configuration:
Chicago> enable
Password: cisco
Chicago# conf t
Chicago(config)# router ospf 10
We need to add Chicago’s S0/1 interface to Area 21
Chicago(config-router)# network 192.168.16.4 0.0.0.3 area 21
Again, area 21 should not receive any external or inter-area routes (except the default route). In order to accomplish this, 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 want to configure area 21 as a totally stubby area.
Chicago(config-router)# area 21 stub no-summary
Chicago(config-router)# end
Chicago# copy run start
The other interface on the Chicago router is already configured correctly in this scenario, as well as the New York router so there is nothing that needs to be done on that router.

4 thoughts on “Lab Simulation 1 – OSPF”

IB says:

03/25/2019 at 12:47 PM

Hello

How was the exam? Pls can you share some of the questions

McFaber says:

03/01/2019 at 7:55 PM

I found this lab on my last exam some days ago, so it could better to focus all together the right answer. Any ideas?

McFaber says:

02/26/2019 at 6:50 PM

The subnet is /30 so 255.255.255.252 then 0.0.0.3 for the ospf network, it include network and broadcast address, do you think is not the most specific? I tried 0.0.0.0 as you report and it work on GNS with other IP, but I’m not so sure. Share your thoughts.
router ospf 1
log-adjacency-changes
area 1 stub
network 192.168.4.5 0.0.0.0 area 1

Gateway of last resort is 192.168.4.6 to network 0.0.0.0
192.168.4.0/30 is subnetted, 1 subnets
C 192.168.4.4 is directly connected, Serial0/0
O*IA 0.0.0.0/0 [110/65] via 192.168.4.6, 00:09:21, Serial0/0

Loopback001 says:

02/26/2019 at 4:22 AM

The most specific wildcard mask possible is:

Seattle:
network 192.168.16.5 0.0.0.0 area 21

Chicago:
network 192.168.16.6 0.0.0.0 area 21

4 thoughts on “Lab Simulation 1 – OSPF”

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