2.7.3 Packet Tracer – OSPF Multiarea Exploration – Physical Mode (Part 2) Answers

2.7.3 Packet Tracer – OSPF Multiarea Exploration – Physical Mode (Part 2) Answers

Objectives

  • Part 1: Evaluate Network Operation of Single-Area OSPF
  • Part 2: Evaluate Network Operation of Multiarea OSPF
  • Part 3: Configure a New Area and Attach to Area 0 Through the Internet

Topology

2.7.3 Packet Tracer - OSPF Multiarea Exploration - Physical Mode (Part 2) Answers 2

Background / Scenario

Part 1: The Beginning

Casual Recording Company, based in Sao Paulo, Brazil, provides self-serve, mini-recording studios around the city so that anyone can rent a timeslot and record their songs by themselves. CRC began with a singlearea OSPF network located in one building. This idea was very popular and consequently the business has grown, causing the company to expand into a branch office in a second building at the far end of the city. They continued to use single-area OSPF. You will evaluate the impact of the expanded network.

Part 2: Business is Booming

The IT department in CRC decided to migrate to a multiarea OSPF network. You will evaluate the impact and benefits derived from the change to determine if it was a good decision or not.

Part 3: CRC Expansion Continues

CRC has continued to grow and will open a new branch office in Montevideo, Uruguay. You will configure the Area Border Router for the new area and physically connect the branch office network to the corporate headquarters network through the internet.

Instructions

Part 2: Evaluate Multiarea OSPF Network Operation

In this part, CRC has migrated their single-area OSPF to multiarea OSPF.

Step 1: Explore OSPF Area 1 devices in the Corporate HQ and Branch Office.

a. Click the city icon for Sao Paulo, and then click Corporate HQ. Click the rack icon that represents the Sao Paulo HQ Wiring Closet.

b. Click A1_ABR1, and then select the CLI tab.

c. The terminal should show that G0/0 and G1/0 are up and that two adjacencies have been established, as shown below. If not, wait for the OSPF loading process to complete.

<output omitted>
Press RETURN to get started!

%LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet1/0, changed state to
up
%LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet0/0, changed state to
up
23:00:40: %OSPF-5-ADJCHG: Process 1, Nbr 172.17.1.2 on GigabitEthernet0/0 from LOADING
to FULL, Loading Done
23:00:45: %OSPF-5-ADJCHG: Process 1, Nbr 192.168.0.9 on GigabitEthernet1/0 from
LOADING to FULL, Loading Done

A1_ABR1>

d. Execute the show ip route command. Notice that the routing table on router A1_ABR1 is shorter than it was on router B1_R5 in the single-area OPSF example in Part 1.

A1_ABR1# show ip route
Codes: C – connected, S – static, I – IGRP, R – RIP, M – mobile, B – BGP
       D – EIGRP, EX – EIGRP external, O – OSPF, IA – OSPF inter area
       N1 – OSPF NSSA external type 1, N2 – OSPF NSSA external type 2
       E1 – OSPF external type 1, E2 – OSPF external type 2, E – EGP
       i – IS-IS, L1 – IS-IS level-1, L2 – IS-IS level-2, ia – IS-IS inter area
       * – candidate default, U – per-user static route, o – ODR
       P – periodic downloaded static route
 
Gateway of last resort is not set
 
O IA 10.0.0.0/8 [110/2] via 172.17.1.2, 00:04:56, GigabitEthernet0/0
     172.17.0.0/30 is subnetted, 1 subnets
C       172.17.1.0 is directly connected, GigabitEthernet0/0
     192.168.0.0/29 is subnetted, 2 subnets
O       192.168.0.0 [110/2] via 192.168.0.9, 00:04:46, GigabitEthernet1/0
C       192.168.0.8 is directly connected, GigabitEthernet1/0
O    192.168.1.0/24 [110/3] via 192.168.0.9, 00:04:46, GigabitEthernet1/0
     192.168.2.0/32 is subnetted, 1 subnets
O       192.168.2.1 [110/3] via 192.168.0.9, 00:04:46, GigabitEthernet1/0
     192.168.3.0/32 is subnetted, 1 subnets
O       192.168.3.1 [110/3] via 192.168.0.9, 00:04:46, GigabitEthernet1/0

How are the networks from Area 51 displayed in the routing table of A1_ABR1?
All of Area 51 networks are displayed as one summarized network.
O IA 10.0.0.0/8 [110/3] via 192.168.0.10, 00:00:10, GigabitEthernet0/0/1

e. Execute the show ip ospf command on router A1_ABR1.

A1_ABR1# show ip ospf
 Routing Process “ospf 1” with ID 172.17.1.1
 Supports only single TOS(TOS0) routes
 Supports opaque LSA
 It is an area border router
 SPF schedule delay 5 secs, Hold time between two SPFs 10 secs
 Minimum LSA interval 5 secs. Minimum LSA arrival 1 secs
 Number of external LSA 0. Checksum Sum 0x000000
 Number of opaque AS LSA 0. Checksum Sum 0x000000
 Number of DCbitless external and opaque AS LSA 0
 Number of DoNotAge external and opaque AS LSA 0
 Number of areas in this router is 2. 2 normal 0 stub 0 nssa
 External flood list length 0
    Area 1
        Number of interfaces in this area is 1
        Area has no authentication
        SPF algorithm executed 3 times
        Area ranges are
        Number of LSA 9. Checksum Sum 0x03c6b4
        Number of opaque link LSA 0. Checksum Sum 0x000000
        Number of DCbitless LSA 0
        Number of indication LSA 0
        Number of DoNotAge LSA 0
        Flood list length 0
    Area BACKBONE(0)
        Number of interfaces in this area is 1
        Area has no authentication
        SPF algorithm executed 5 times
        Area ranges are
        Number of LSA 9. Checksum Sum 0x030408
        Number of opaque link LSA 0. Checksum Sum 0x000000
        Number of DCbitless LSA 0
        Number of indication LSA 0
        Number of DoNotAge LSA 0
        Flood list length 0

Which areas are displayed on router A1_ABR1?
The backbone area 1 and area 0 are displayed.

Record the number of times that the SPF algorithm has been executed in each area.
Most likely 3 times for Area 1 and 5 times for Area 0, but answers may vary.

f. Keep the console window for A1_ABR1 open and select router A1_R2. Execute the show ip route and show ip ospf commands, and then compare the output with the output on A1_ABR1. Similar networks should be displayed and the number of SPF algorithm executions should be similar.

A1_R2> show ip route
Codes: L – local, C – connected, S – static, R – RIP, M – mobile, B – BGP
       D – EIGRP, EX – EIGRP external, O – OSPF, IA – OSPF inter area
       N1 – OSPF NSSA external type 1, N2 – OSPF NSSA external type 2
       E1 – OSPF external type 1, E2 – OSPF external type 2, E – EGP
       i – IS-IS, L1 – IS-IS level-1, L2 – IS-IS level-2, ia – IS-IS inter area
       * – candidate default, U – per-user static route, o – ODR
       P – periodic downloaded static route
 
Gateway of last resort is not set
 
O IA 10.0.0.0/8 [110/4] via 192.168.0.4, 00:12:02, GigabitEthernet0/0/0
     172.17.0.0/30 is subnetted, 1 subnets
O IA    172.17.1.0/30 [110/3] via 192.168.0.4, 00:12:02, GigabitEthernet0/0/0
     192.168.0.0/24 is variably subnetted, 3 subnets, 2 masks
C       192.168.0.0/29 is directly connected, GigabitEthernet0/0/0
L       192.168.0.2/32 is directly connected, GigabitEthernet0/0/0
O       192.168.0.8/29 [110/2] via 192.168.0.4, 00:12:02, GigabitEthernet0/0/0
O    192.168.1.0/24 [110/2] via 192.168.0.1, 00:12:02, GigabitEthernet0/0/0
     192.168.2.0/24 is variably subnetted, 2 subnets, 2 masks
C       192.168.2.0/24 is directly connected, Loopback0
L       192.168.2.1/32 is directly connected, Loopback0
     192.168.3.0/32 is subnetted, 1 subnets
O       192.168.3.1/32 [110/2] via 192.168.0.3, 00:12:02, GigabitEthernet0/0/0
 
A1_R2> show ip ospf
 Routing Process “ospf 1” with ID 192.168.2.1
 Supports only single TOS(TOS0) routes
 Supports opaque LSA
 SPF schedule delay 5 secs, Hold time between two SPFs 10 secs
 Minimum LSA interval 5 secs. Minimum LSA arrival 1 secs
 Number of external LSA 0. Checksum Sum 0x000000
 Number of opaque AS LSA 0. Checksum Sum 0x000000
 Number of DCbitless external and opaque AS LSA 0
 Number of DoNotAge external and opaque AS LSA 0
 Number of areas in this router is 1. 1 normal 0 stub 0 nssa
 External flood list length 0
    Area 1
        Number of interfaces in this area is 2
        Area has no authentication
        SPF algorithm executed 5 times
        Area ranges are
        Number of LSA 9. Checksum Sum 0x03c6b4
        Number of opaque link LSA 0. Checksum Sum 0x000000
        Number of DCbitless LSA 0
        Number of indication LSA 0
        Number of DoNotAge LSA 0
        Flood list length 0

Record the number of SPF algorithm executions.
In Packet Tracer, answers will vary.

Step 2: Explore the impact of changes in Area 51.

a. Keep the console windows open for both routers A1_ABR1 and A1_R2.
b. On the blue tool bar at the top, click the Back level button twice to return to the Sao Paulo city view. You can also use the shortcut keys Alt+Left arrow key.

c. Click Branch Office, and then the rack icon that represents the Sao Paulo Branch Office Wiring Closet.

d. Click A51_R4, and then select the CLI tab.

e. The terminal should show that all four Gigabit Ethernet interfaces are up and that four adjacencies have been established.

<output omitted>
Press RETURN to get started!

%LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet4/0, changed state to
up
%LINK-5-CHANGED: Interface GigabitEthernet1/0, changed state to up
%LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet1/0, changed state to
up
%LINK-5-CHANGED: Interface GigabitEthernet2/0, changed state to up
%LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet2/0, changed state to
up
%LINK-5-CHANGED: Interface GigabitEthernet3/0, changed state to up
%LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet3/0, changed state to
up
23:00:40: %OSPF-5-ADJCHG: Process 1, Nbr 1.1.1.1 on GigabitEthernet1/0 from LOADING to
FULL, Loading Done
23:00:40: %OSPF-5-ADJCHG: Process 1, Nbr 172.17.1.2 on GigabitEthernet4/0 from LOADING
to FULL, Loading Done
23:00:40: %OSPF-5-ADJCHG: Process 1, Nbr 3.3.3.3 on GigabitEthernet3/0 from LOADING to
FULL, Loading Done
23:00:45: %OSPF-5-ADJCHG: Process 1, Nbr 2.2.2.2 on GigabitEthernet2/0 from LOADING to
FULL, Loading Done

A51_R4>

f. Execute the show ip route command. Compare the output of A51_R4 to the output of A1_ABR1 and A1_R2. Notice that other than a few connected or local routes, the same networks are displayed.

A51_R4# show ip route
Codes: C – connected, S – static, I – IGRP, R – RIP, M – mobile, B – BGP
       D – EIGRP, EX – EIGRP external, O – OSPF, IA – OSPF inter area
       N1 – OSPF NSSA external type 1, N2 – OSPF NSSA external type 2
       E1 – OSPF external type 1, E2 – OSPF external type 2, E – EGP
       i – IS-IS, L1 – IS-IS level-1, L2 – IS-IS level-2, ia – IS-IS inter area
       * – candidate default, U – per-user static route, o – ODR
       P – periodic downloaded static route
 
Gateway of last resort is not set
 
     10.0.0.0/8 is variably subnetted, 8 subnets, 3 masks
C       10.10.0.0/30 is directly connected, GigabitEthernet4/0
C       10.10.0.4/30 is directly connected, GigabitEthernet3/0
C       10.10.0.8/30 is directly connected, GigabitEthernet1/0
O       10.10.0.12/30 [110/2] via 10.10.0.22, 00:20:53, GigabitEthernet2/0
                      [110/2] via 10.10.0.6, 00:20:53, GigabitEthernet3/0
O       10.10.0.16/30 [110/2] via 10.10.0.10, 00:20:53, GigabitEthernet1/0
                      [110/2] via 10.10.0.22, 00:20:53, GigabitEthernet2/0
C       10.10.0.20/30 is directly connected, GigabitEthernet2/0
O       10.20.0.1/32 [110/2] via 10.10.0.22, 00:20:53, GigabitEthernet2/0
O       10.20.4.0/24 [110/2] via 10.10.0.22, 00:20:53, GigabitEthernet2/0
     172.17.0.0/30 is subnetted, 1 subnets
O IA    172.17.1.0 [110/2] via 10.10.0.2, 00:20:53, GigabitEthernet4/0
     192.168.0.0/29 is subnetted, 2 subnets
O IA    192.168.0.0 [110/4] via 10.10.0.2, 00:20:28, GigabitEthernet4/0
O IA    192.168.0.8 [110/3] via 10.10.0.2, 00:20:38, GigabitEthernet4/0
O IA 192.168.1.0/24 [110/5] via 10.10.0.2, 00:20:28, GigabitEthernet4/0
     192.168.2.0/32 is subnetted, 1 subnets
O IA    192.168.2.1 [110/5] via 10.10.0.2, 00:20:28, GigabitEthernet4/0
     192.168.3.0/32 is subnetted, 1 subnets
O IA    192.168.3.1 [110/5] via 10.10.0.2, 00:20:28, GigabitEthernet4/0
 
A51_R4>

Record the number of IA routes displayed.
6 IA routes are displayed.

g. Execute the show ip ospf command.

A51_R4# show ip ospf
 Routing Process “ospf 1” with ID 4.4.4.4
 Supports only single TOS(TOS0) routes
 Supports opaque LSA
 SPF schedule delay 5 secs, Hold time between two SPFs 10 secs
 Minimum LSA interval 5 secs. Minimum LSA arrival 1 secs
 Number of external LSA 0. Checksum Sum 0x000000
 Number of opaque AS LSA 0. Checksum Sum 0x000000
 Number of DCbitless external and opaque AS LSA 0
 Number of DoNotAge external and opaque AS LSA 0
 Number of areas in this router is 1. 1 normal 0 stub 0 nssa
 External flood list length 0
    Area 51
        Number of interfaces in this area is 4
        Area has no authentication
        SPF algorithm executed 4 times
        Area ranges are
        Number of LSA 17. Checksum Sum 0x04ea4a
        Number of opaque link LSA 0. Checksum Sum 0x000000
        Number of DCbitless LSA 0
        Number of indication LSA 0
        Number of DoNotAge LSA 0
        Flood list length 0

Record the number of SPF calculations.
In Packet Tracer, answers will vary.

h. Keep the console window for A51_R4 open. Click A51_R2. On the Physical tab, turn the power off to simulate a power failure.

i. Return to the console window for A51_R4. You should see a console message that the adjacency with A51_R2 is down.

%LINK-3-UPDOWN: Interface GigabitEthernet2/0, changed state to down
%LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet2/0, changed state to
down
23:30:33: %OSPF-5-ADJCHG: Process 1, Nbr 2.2.2.2 on GigabitEthernet2/0 from FULL to
DOWN, Neighbor Down: Interface down or detached

j. Re-issue the show ip route and show ip ospf commands.

A51_R4# show ip route
Codes: C – connected, S – static, I – IGRP, R – RIP, M – mobile, B – BGP
       D – EIGRP, EX – EIGRP external, O – OSPF, IA – OSPF inter area
       N1 – OSPF NSSA external type 1, N2 – OSPF NSSA external type 2
       E1 – OSPF external type 1, E2 – OSPF external type 2, E – EGP
       i – IS-IS, L1 – IS-IS level-1, L2 – IS-IS level-2, ia – IS-IS inter area
       * – candidate default, U – per-user static route, o – ODR
       P – periodic downloaded static route
 
Gateway of last resort is not set
 
     10.0.0.0/30 is subnetted, 3 subnets
C       10.10.0.0 is directly connected, GigabitEthernet4/0
C       10.10.0.4 is directly connected, GigabitEthernet3/0
C       10.10.0.8 is directly connected, GigabitEthernet1/0
     172.17.0.0/30 is subnetted, 1 subnets
O IA    172.17.1.0 [110/2] via 10.10.0.2, 00:31:09, GigabitEthernet4/0
     192.168.0.0/29 is subnetted, 2 subnets
O IA    192.168.0.0 [110/4] via 10.10.0.2, 00:30:44, GigabitEthernet4/0
O IA    192.168.0.8 [110/3] via 10.10.0.2, 00:30:54, GigabitEthernet4/0
O IA 192.168.1.0/24 [110/5] via 10.10.0.2, 00:30:44, GigabitEthernet4/0
     192.168.2.0/32 is subnetted, 1 subnets
O IA    192.168.2.1 [110/5] via 10.10.0.2, 00:30:44, GigabitEthernet4/0
     192.168.3.0/32 is subnetted, 1 subnets
O IA    192.168.3.1 [110/5] via 10.10.0.2, 00:30:44, GigabitEthernet4/0
 
A51_R4# show ip ospf
 Routing Process “ospf 1” with ID 4.4.4.4
 Supports only single TOS(TOS0) routes
 Supports opaque LSA
 SPF schedule delay 5 secs, Hold time between two SPFs 10 secs
 Minimum LSA interval 5 secs. Minimum LSA arrival 1 secs
 Number of external LSA 0. Checksum Sum 0x000000
 Number of opaque AS LSA 0. Checksum Sum 0x000000
 Number of DCbitless external and opaque AS LSA 0
 Number of DoNotAge external and opaque AS LSA 0
 Number of areas in this router is 1. 1 normal 0 stub 0 nssa
External flood list length 0
    Area 51
        Number of interfaces in this area is 3
        Area has no authentication
        SPF algorithm executed 5 times
        Area ranges are
        Number of LSA 15. Checksum Sum 0x069e7f
        Number of opaque link LSA 0. Checksum Sum 0x000000
        Number of DCbitless LSA 0
        Number of indication LSA 0
        Number of DoNotAge LSA 0
        Flood list length 0

Have the SPF algorithm executions increased?
Yes

Record the number of SPF algorithm executions.
In Packet Tracer, answers will vary.

What networks are missing from the A51_R4 routing table?
All networks that were advertised by A51_R2 are missing.

k. Navigate to A1_R2 and issue the show ip route and show ip ospf commands again.

A1_R2# show ip route
Codes: L – local, C – connected, S – static, R – RIP, M – mobile, B – BGP
       D – EIGRP, EX – EIGRP external, O – OSPF, IA – OSPF inter area
       N1 – OSPF NSSA external type 1, N2 – OSPF NSSA external type 2
       E1 – OSPF external type 1, E2 – OSPF external type 2, E – EGP
       i – IS-IS, L1 – IS-IS level-1, L2 – IS-IS level-2, ia – IS-IS inter area
       * – candidate default, U – per-user static route, o – ODR
       P – periodic downloaded static route
 
Gateway of last resort is not set
 
O IA 10.0.0.0/8 [110/4] via 192.168.0.4, 00:33:22, GigabitEthernet0/0/0
     172.17.0.0/30 is subnetted, 1 subnets
O IA    172.17.1.0/30 [110/3] via 192.168.0.4, 00:33:22, GigabitEthernet0/0/0
     192.168.0.0/24 is variably subnetted, 3 subnets, 2 masks
C       192.168.0.0/29 is directly connected, GigabitEthernet0/0/0
L       192.168.0.2/32 is directly connected, GigabitEthernet0/0/0
O       192.168.0.8/29 [110/2] via 192.168.0.4, 00:33:22, GigabitEthernet0/0/0
O    192.168.1.0/24 [110/2] via 192.168.0.1, 00:33:22, GigabitEthernet0/0/0
     192.168.2.0/24 is variably subnetted, 2 subnets, 2 masks
C       192.168.2.0/24 is directly connected, Loopback0
L       192.168.2.1/32 is directly connected, Loopback0
     192.168.3.0/32 is subnetted, 1 subnets
O       192.168.3.1/32 [110/2] via 192.168.0.3, 00:33:22, GigabitEthernet0/0/0
 
A1_R2# show ip ospf
 Routing Process “ospf 1” with ID 192.168.2.1
 Supports only single TOS(TOS0) routes
 Supports opaque LSA
 SPF schedule delay 5 secs, Hold time between two SPFs 10 secs
 Minimum LSA interval 5 secs. Minimum LSA arrival 1 secs
 Number of external LSA 0. Checksum Sum 0x000000
 Number of opaque AS LSA 0. Checksum Sum 0x000000
 Number of DCbitless external and opaque AS LSA 0
 Number of DoNotAge external and opaque AS LSA 0
 Number of areas in this router is 1. 1 normal 0 stub 0 nssa
 External flood list length 0
    Area 1
        Number of interfaces in this area is 2
        Area has no authentication
        SPF algorithm executed 6 times
        Area ranges are
        Number of LSA 9. Checksum Sum 0x039fe8
        Number of opaque link LSA 0. Checksum Sum 0x000000
        Number of DCbitless LSA 0
        Number of indication LSA 0
        Number of DoNotAge LSA 0
        Flood list length 0
 
A1_R2#

Is the summary route for Area 51 still in the routing table?
Yes.

Has the value for the SPF algorithm executions increased from Step 1g?
The answer should be no. However, the number of executions may have changed if the student deviated from the instructions and performed an action that would cause addition SPF calculations such as reloading a router or shutting down an interface in Area 1.

Will a ping or a tracert between A1_PC1 (192.168.1.10) and A51_PC1 (10.20.4.10) be successful?
No. A ping from A1_PC1 to A51_PC1 should fail. A tracert from A1_PC1 to A51_PC1 should stop at A51_ABR1.

Note: The area 51 border router, A51_ABR1 has summarized the 10.0.0.0/8 networks and is advertising the summary route to all the other areas. Topology changes in area 51, such as power failures, interface disconnects, or OSPF network changes, will cause SPF recalculations on all routers within area 51 but will NOT cause SPF recalculations in area 1.

Step 3: Summarize the Area 1 routes to be sent to Area 51.

a. Select router A51_R4 and execute the show ip route.

Compare the output of A51_R4 to the output of A1_R4. You should notice that all of the 192.168.0.0 networks from area 1 are showing inside the routing table.

If a cleaning crew accidentally removed the cable on A1_R1 (192.168.1.0/24), how will the routers in area 51 be affected?
All area 51 routers would have SPF algorithm executions and would have to update their routing tables.

What could be done to avoid the area 51 recalculations?
Router A1_ABR1 should summarize the 192.168.0.0/16 networks of area 1.

b. Navigate to A1_ABR1. Using the CLI tab, enter the following commands to implement OSPF summarization for the 192.168.0.0 network in area 1:

A1_ABR1(config)# router ospf 1
A1_ABR1(config-router)# area 1 range 192.168.0.0 255.255.0.0
A1_ABR1(config-router)# end

Note: Summarizing OSPF routes is beyond the scope of this course and the CCNA exam.

c. Return to the screen of A51_R4 and execute a show ip route command.

How is the routing table output different following the summarization?
The networks from area 1 are all summarized with an interarea route:
IA 192.168.0.0/16 [110/4] via 10.10.0.21, 00:14:04, GigabitEthernet2/0

Note: Multiarea OSPF provides the benefit of summarization between areas. The summarization helps to reduce the size of routing tables and reduces the frequency of LSA flooding throughout the entire system. With summarization, a change in one area will cause all routers within that area to execute SPF. Routing tables and SPF recalculations for routers in other areas will not be affected. Connectivity to the downed network(s) still poses an issue.

You have completed Part 2: Evaluate Multiarea OSPF Network Operation.

To continue to Part 3: Configure a New Area and Attach to Area 0 Through the Internet, close this Packet Tracer file. Return to the online course and open the Multiarea OSPF Exploration – Physical Mode (Part3) Packet Tracer file.

Download 2.7.3 Packet Tracer – OSPF Multiarea Exploration – Physical Mode (Part 2) Completed:


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