Course:
CCNP ENARSI Labs
In this part, you will implement multiarea OSPF. Multiarea OSPF defines a two-layer area hierarchy using a backbone area interconnecting regular areas. This is useful in larger network deployments to reduce processing and memory overhead.
In this topology, OSPF has the following three areas defined:
· Area 0 – The backbone area. All regular areas should connect to the backbone area.
· Area 1 and Area 2 – Regular OSPF areas that connect to the backbone area.
The routers and switches in the topology are used in the following roles:
· Internal routers – R2 is an internal router in Area 0, D1 is internal in Area 1, and D2 is internal in Area 2.
· Backbone routers – R1, R2, and R3 are backbone routers as they all have interfaces in Area 0.
· Area Border routers (ABRs) – R1 and R3 are ABRs because they connect regular areas (i.e., Area 1 and Area 2) to the backbone Area 0.
· Autonomous System Boundary router (ASBR) – R2 is an ASBR because it connects to another non-OSPF network.
Recall that OSPF can be enabled using the traditional network router configuration command or by using the ip ospf process-id area area-id interface configuration command. Although the interface method is simpler, the OSPF routing configuration commands are applied to individual interfaces and not conveniently found in a central location. Therefore, in this lab, we will implement multiarea OSPF using wildcard masks.
You will now configure multiarea OSPF on all five devices starting with D1. You will also configure router IDs, reference bandwidths, and default route propagation.
Note: The verification output displayed in the following part assumes that the devices have been configured in the prescribed order. The output will vary if all devices are configured simultaneously.
D1 will advertise its OSPF networks using the network router configuration command and wildcard masks. D1 is an internal router in Area 1. Therefore, both network commands will be configured for Area 1.
a. Layer 3 switches are not enabled to perform routing by default. Therefore, routing must be enabled using the ip routing global configuration command.
Open configuration window
| D1(config)# ip routing |
b. Next, enter the OSPF router configuration mode using process ID 123, assign D1 the router ID 1.1.1.2. You will also set the reference bandwidth to distinguish between Gigabit Ethernet and FastEthernet interfaces. Changing the reference bandwidth to a higher value allows for a differentiation of cost between higher-speed interfaces.
D1(config)# router ospf 123 D1(config-router)# router-id 1.1.1.2 D1(config-router)# auto-cost reference-bandwidth 10000 % OSPF: Reference bandwidth is changed. Please ensure reference bandwidth is consistent across all routers. |
Note: Setting the reference cost value too high may cause issues with low-bandwidth interfaces.
c. Configure D1 to advertise the Gi0/1 interface 10.10.0.0/30 network in OSPF Area 1. The wildcard mask can be calculated by deducting the subnet mask (i.e., /30 = 255.255.255.252) from 255.255.255.255, resulting in a wildcard mask of 0.0.0.3.
| D1(config-router)# network 10.10.0.0 0.0.0.3 area 1 |
d. Next, configure D1 to advertise its Gi0/3 interface 10.10.1.0/24 network in OSPF Area 1 and return to privileged EXEC mode.
D1(config-router)# network 10.10.1.0 0.0.0.255 area 1 D1(config-router)# end |
e. Verify the OSPF configuration on D1 using the show ip protocols command.
D1# show ip protocols *** IP Routing is NSF aware ***
Routing Protocol is “ospf 123” Outgoing update filter list for all interfaces is not set Incoming update filter list for all interfaces is not set Router ID 1.1.1.2 Number of areas in this router is 1. 1 normal 0 stub 0 nssa Maximum path: 4 Routing for Networks: 10.10.0.0 0.0.0.3 area 1 10.10.1.0 0.0.0.255 area 1 Routing Information Sources: Gateway Distance Last Update Distance: (default is 110) |
The output confirms the router ID, and the number of areas, and the networks advertised. Notice there are no Routing Information Sources because there are no OSPF neighbors
f. Verify the OSPF interfaces using the show ip ospf interface brief command.
D1# show ip ospf interface brief Interface PID Area IP Address/Mask Cost State Nbrs F/C Gi0/3 123 1 10.10.1.1/24 10 DR 0/0 Gi0/1 123 1 10.10.0.2/30 10 DR 0/0 |
The output confirms that both G0/1 and G0/3 interfaces were correctly assigned to Area 1
e. Finally, verify the OSPF routes in the routing table using the show ip route ospf command.
| D1# show ip route ospf |
Notice that no routes are displayed. This is because D1 does not yet have an OSPF neighbor.
Next, configure R1. R1 is an ABR with an interface in Area 1 and the other interface in the backbone.
a. Enter the OSPF router configuration mode using process ID 123, assign R1 the router ID 1.1.1.1, and set the reference bandwidth to distinguish between Gigabit Ethernet and FastEthernet interfaces.
Open configuration window
R1(config)# router ospf 123 R1(config-router)# router-id 1.1.1.1 R1(config-router)# auto-cost reference-bandwidth 10000 % OSPF: Reference bandwidth is changed. Please ensure reference bandwidth is consistent across all routers. |
b. Configure R1 to advertise the G0/0 interface 172.16.0.0/30 network in OSPF Area 0.
| R1(config-router)# network 172.16.0.0 0.0.0.3 area 0 |
c. Advertise the G0/1 interface 10.10.0.0/30 network in OSPF Area 1 and return to privileged EXEC mode.
R1(config-router)# network 10.10.0.0 0.0.0.3 area 1 R1(config-router)# end *Jan 4 11:55:32.064: %OSPF-5-ADJCHG: Process 123, Nbr 1.1.1.2 on GigabitEthernet0/1 from LOADING to FULL, Loading Done |
Notice the informational message stating that a neighbor adjacency has been established with D1 (i.e., 1.1.1.2).
d. Verify the OSPF configuration on R1 using the show ip protocols command.
R1# show ip protocols | begin ospf Routing Protocol is “ospf 123” Outgoing update filter list for all interfaces is not set Incoming update filter list for all interfaces is not set Router ID 1.1.1.1 It is an area border router Number of areas in this router is 2. 2 normal 0 stub 0 nssa Maximum path: 4 Routing for Networks: 10.10.0.0 0.0.0.3 area 1 172.16.0.0 0.0.0.3 area 0 Routing Information Sources: Gateway Distance Last Update 1.1.1.2 110 00:07:55 Distance: (default is 110) |
Like the previous output of D1, this output confirms the router ID, and the networks advertised. However, notice that it also explicitly states that R1 is an area border router (ABR), that it is in two areas, and that it has established an adjacency and exchanged routing information with D2 (i.e., 1.1.1.2).
e. Verify that the reference bandwidth has been changed using the show ip ospf | begin Ref command.
R1# show ip ospf | begin Ref Reference bandwidth unit is 10000 mbps Area BACKBONE(0) (Inactive) Number of interfaces in this area is 1 Area has no authentication SPF algorithm last executed 00:14:41.606 ago SPF algorithm executed 2 times Area ranges are Number of LSA 3. Checksum Sum 0x01ABED 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 1 Number of interfaces in this area is 1 Area has no authentication SPF algorithm last executed 00:15:07.141 ago SPF algorithm executed 5 times Area ranges are Number of LSA 4. Checksum Sum 0x0292B8 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 |
The output confirms that the reference bandwidth has been changed to distinguish GigabitEthernet interfaces. The output also confirms that R1 is in two areas and has two link-state databases (LSDBs).
Note: Area 0 is currently inactive because there are no other peers configured yet.
f. Verify the active OSPF interfaces and assigned areas using the show ip ospf interface brief command.
R1# show ip ospf interface brief Interface PID Area IP Address/Mask Cost State Nbrs F/C Gi0/0 123 0 172.16.0.2/30 1 DR 0/0 Gi0/1 123 1 10.10.0.1/30 1 BDR 1/1 |
The output confirms the interfaces, areas, and IP addresses.
g. Verify which OSPF neighbors R1 has established an adjacency with using the show ip ospf neighbor command.
R1# show ip ospf neighbor Neighbor ID Pri State Dead Time Address Interface 1.1.1.2 1 FULL/DR 00:00:31 10.10.0.2 GigabitEthernet0/1 |
The output confirms that R1 has one neighbor (i.e., 1.1.1.2 = D1), they have a full adjacency established, the IP address of D1 is 10.10.0.2, and R1 can reach D1 using its G0/1 interface.
h. Use the show ip ospf neighbor detail command to get additional information about neighbor adjacencies.
R1# show ip ospf neighbor detail Neighbor 1.1.1.2, interface address 10.10.0.2, interface-id 38 In the area 1 via interface GigabitEthernet0/1 Neighbor priority is 1, State is FULL, 6 state changes DR is 10.10.0.2 BDR is 10.10.0.1 Options is 0x12 in Hello (E-bit, L-bit) Options is 0x52 in DBD (E-bit, L-bit, O-bit) LLS Options is 0x1 (LR) Dead timer due in 00:00:34 Neighbor is up for 00:19:09 Index 1/1/1, retransmission queue length 0, number of retransmission 0 First 0x0(0)/0x0(0)/0x0(0) Next 0x0(0)/0x0(0)/0x0(0) Last retransmission scan length is 0, maximum is 0 Last retransmission scan time is 0 msec, maximum is 0 msec |
As shown, the output confirms various information about the OSPF neighbor including DR and BDR status.
i. Verify the OSPF routes in the routing table using the show ip route ospf command.
R1# show ip route ospf | begin Gateway Gateway of last resort is not set
10.0.0.0/8 is variably subnetted, 3 subnets, 3 masks O 10.10.1.0/24 [110/11] via 10.10.0.2, 00:24:43, GigabitEthernet0/1 |
The output displays an entry for the D1 LAN. The O designation identifies this as an OSPF internal route. Network routes learned from other OSPF routers in the same area are known as intra-area routes and are identified in the IP routing table with an O.
j. Finally, get detailed information on how R1 learned about the OSPF entry using the show ip route ospf 10.10.1.0 command.
R1# show ip route 10.10.1.0 Routing entry for 10.10.1.0/24 Known via “ospf 123“, distance 110, metric 11, type intra area Last update from 10.10.0.2 on GigabitEthernet0/1, 00:25:25 ago Routing Descriptor Blocks: * 10.10.0.2, from 1.1.1.2, 00:25:25 ago, via GigabitEthernet0/1 Route metric is 11, traffic share count is 1 |
The output confirms that R1 learned about the intra-area route 10.10.1.0 from 10.10.0.2 with a router ID of 1.1.1.2 in OSPF 123.
Next, configure is R2. R2 is an internal backbone router and will become an ASBR.
a. Enter the OSPF router configuration mode using process ID 123, assign R2 the router ID 2.2.2.1, and set the reference bandwidth to distinguish between Gigabit Ethernet and FastEthernet interfaces.
Open configuration window
R2(config)# router ospf 123 R2(config-router)# router-id 2.2.2.1 R2(config-router)# auto-cost reference-bandwidth 10000 % OSPF: Reference bandwidth is changed. Please ensure reference bandwidth is consistent across all routers. |
b. Configure R2 to advertise its two interfaces in OSPF Area 0.
R2(config-router)# network 172.16.0.0 0.0.0.3 area 0 R2(config-router)# network 172.16.1.0 0.0.0.3 area 0 *Dec 28 16:22:42.530: %OSPF-5-ADJCHG: Process 123, Nbr 1.1.1.1 on GigabitEthernet0/0 from LOADING to FULL, Loading Done |
The output confirms that an adjacency has been established with R1 (i.e., 1.1.1.1).
Note: Alternatively, the two network statements could be combined using network 17.16.0.0 0.0.1.3 area 0.
c. Configure R2 to propagate a default route to the internet. In our lab, the internet is represented as a loopback interface.
R2(config-router)# default-information originate R2(config-router)# exit R2(config)# ip route 0.0.0.0 0.0.0.0 lo0 %Default route without gateway, if not a point-to-point interface, may impact performance R2(config)# exit |
d. Verify the OSPF configuration on R2 using the show ip protocols command.
R2# show ip protocols | begin ospf Routing Protocol is “ospf 123” Outgoing update filter list for all interfaces is not set Incoming update filter list for all interfaces is not set Router ID 2.2.2.1 It is an autonomous system boundary router Redistributing External Routes from, Number of areas in this router is 1. 1 normal 0 stub 0 nssa Maximum path: 4 Routing for Networks: 172.16.0.0 0.0.0.3 area 0 172.16.1.0 0.0.0.3 area 0 Routing Information Sources: Gateway Distance Last Update 1.1.1.1 110 00:24:29 Distance: (default is 110) |
Again, this output confirms the router ID chosen, number of areas R2 is in (i.e., 1), networks advertised, and that it has established an adjacency and exchanged routing information with R1 (i.e., 1.1.1.1). R2 does not have an adjacency with D1 because it is in another area.
Notice as well, that it explicitly states that R2 is an autonomous system boundary router (ASBR). This is because it is now propagating a default route to all other routers in the OSPF domain.
e. Verify that the reference bandwidth has been changed using the show ip ospf | begin Ref command as shown.
R2# show ip ospf | begin Ref Reference bandwidth unit is 10000 mbps Area BACKBONE(0) Number of interfaces in this area is 2 Area has no authentication SPF algorithm last executed 00:02:27.531 ago SPF algorithm executed 5 times Area ranges are Number of LSA 5. Checksum Sum 0x01C25B 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 |
The output confirms that the reference bandwidth has been changed and also confirms that R2 has two interfaces in its link-state database (LSDB).
f. Verify the active OSPF interfaces and assigned areas using the show ip ospf interface brief command.
R2# show ip ospf interface brief Interface PID Area IP Address/Mask Cost State Nbrs F/C Gi0/1 123 0 172.16.1.1/30 1 DR 0/0 Gi0/0 123 0 172.16.0.1/30 1 BDR 1/1 |
The output confirms that the two interfaces are in Area 0, their IP addresses, state, and neighbors.
g. Verify which OSPF neighbors R2 has established an adjacency using the show ip ospf neighbor command.
R2# show ip ospf neighbor
Neighbor ID Pri State Dead Time Address Interface 1.1.1.1 1 FULL/DR 00:00:36 172.16.0.2 GigabitEthernet0/0 |
The output confirms that R2 has one neighbor (i.e., 1.1.1.1 = R1) and they have a full adjacency established.
h. Use the show ip ospf neighbor detail command to get additional information about neighbor adjacencies.
R2# show ip ospf neigh detail Neighbor 1.1.1.1, interface address 172.16.0.2 In the area 0 via interface GigabitEthernet0/0 Neighbor priority is 1, State is FULL, 6 state changes DR is 172.16.0.2 BDR is 172.16.0.1 Options is 0x12 in Hello (E-bit, L-bit) Options is 0x52 in DBD (E-bit, L-bit, O-bit) LLS Options is 0x1 (LR) Dead timer due in 00:00:34 Neighbor is up for 00:27:48 Index 1/1/1, retransmission queue length 0, number of retransmission 0 First 0x0(0)/0x0(0)/0x0(0) Next 0x0(0)/0x0(0)/0x0(0) Last retransmission scan length is 0, maximum is 0 Last retransmission scan time is 0 msec, maximum is 0 msec |
As shown, the output confirms various information about the OSPF neighbor including DR and BDR status.
i. Verify the OSPF routes in the routing table using the show ip route ospf command.
R2# show ip route ospf | begin Gateway
Gateway of last resort is 0.0.0.0 to network 0.0.0.0
10.0.0.0/8 is variably subnetted, 2 subnets, 2 masks O IA 10.10.0.0/30 [110/2] via 172.16.0.2, 00:28:19, GigabitEthernet0/0 O IA 10.10.1.0/24 [110/12] via 172.16.0.2, 00:28:19, GigabitEthernet0/0 |
The output displays that there is now a default gateway and two entries for the OSPF Area 1 networks. Notice how these routes are identified as O IA which means they are routes from another area. Network routes learned from OSPF routers in another area using an ABR are known as interarea routes as opposed to intra-area routes.
j. Verify the static route entry in the routing table.
R2# show ip route static | begin Gateway Gateway of last resort is 0.0.0.0 to network 0.0.0.0
S* 0.0.0.0/0 is directly connected, Loopback0 |
k. Finally, get detailed information on how R2 learned about the OSPF entry using the show ip route ospf 10.10.1.0 command.
R2# show ip route 10.10.1.0 Routing entry for 10.10.1.0/24 Known via “ospf 123”, distance 110, metric 12, type inter area Last update from 172.16.0.2 on GigabitEthernet0/0/0, 00:31:08 ago Routing Descriptor Blocks: * 172.16.0.2, from 1.1.1.1, 00:31:08 ago, via GigabitEthernet0/0/0 Route metric is 12, traffic share count is 1 |
The output confirms that R2 learned about the interarea route 10.10.1.0 from OSPF 123 and specifically from R1, based on the router ID of 1.1.1.1.
Next to configure is R3. Like R1, R3 is an ABR with an interface in Area 0 and one in Area 2.
a. Enter the OSPF router configuration mode using process ID 123, assign R3 the router ID 3.3.3.1, and set the reference bandwidth to distinguish between Gigabit Ethernet and FastEthernet interfaces.
Open configuration window
R3(config)# router ospf 123 R3(config-router)# router-id 3.3.3.1 R3(config-router)# auto-cost reference-bandwidth 10000 % OSPF: Reference bandwidth is changed. Please ensure reference bandwidth is consistent across all routers. |
b. Configure R3 to advertise its interfaces in OSPF Area 0 and Area 2 accordingly and then return to privileged EXEC mode.
R3(config-router)# network 172.16.1.0 0.0.0.3 area 0 R3(config-router)# network 10.10.4.0 0.0.0.3 area 2 R3(config-router)# end R3# *Jan 5 19:28:25.146: %OSPF-5-ADJCHG: Process 123, Nbr 2.2.2.1 on GigabitEthernet0/1 from LOADING to FULL, Loading Done |
c. Verify the OSPF configuration on R3 using the show ip protocols command.
R3# show ip protocols | begin ospf Routing Protocol is “ospf 123” Outgoing update filter list for all interfaces is not set Incoming update filter list for all interfaces is not set Router ID 3.3.3.1 It is an area border router Number of areas in this router is 2. 2 normal 0 stub 0 nssa Maximum path: 4 Routing for Networks: 10.10.4.0 0.0.0.3 area 2 172.16.1.0 0.0.0.3 area 0 Routing Information Sources: Gateway Distance Last Update 1.1.1.1 110 00:01:43 2.2.2.1 110 00:01:43 Distance: (default is 110) |
The output confirms the router ID, and that R3 is an ABR, it has interfaces in two areas, the networks it is advertising, and that R3 has R1 (i.e., 1.1.1.1) and R2 (i.e., 2.2.2.1) as sources of routing information.
d. Verify that the reference bandwidth has been changed using the show ip ospf | begin Ref command as shown.
R3# show ip ospf | begin Ref Reference bandwidth unit is 10000 mbps Area BACKBONE(0) Number of interfaces in this area is 1 Area has no authentication SPF algorithm last executed 00:10:38.256 ago SPF algorithm executed 4 times Area ranges are Number of LSA 8. Checksum Sum 0x0396BA 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 2 Number of interfaces in this area is 1 Area has no authentication SPF algorithm last executed 00:10:13.755 ago SPF algorithm executed 2 times Area ranges are Number of LSA 6. Checksum Sum 0x0362CF 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 |
The output confirms that the reference bandwidth has been changed and also confirms that R2 has area information for Area 0 and Area 2.
e. Verify the active OSPF interfaces and assigned areas using the show ip ospf interface brief command.
R3# show ip ospf interface brief Interface PID Area IP Address/Mask Cost State Nbrs F/C Gi0/1 123 0 172.16.1.2/30 1 BDR 1/1 Gi0/2 123 2 10.10.4.1/30 1 DR 0/0 |
The output confirms the interfaces, process ID, areas, IP addresses, cost, state, and neighbors.
f. Verify which OSPF neighbors R2 has established an adjacency with using the show ip ospf neighbor command.
R3# show ip ospf neighbor Neighbor ID Pri State Dead Time Address Interface 2.2.2.1 1 FULL/DR 00:00:31 172.16.1.1 GigabitEthernet0/1 |
The output confirms that R3 has one neighbor (i.e., 2.2.2.1= R2) and they have a full adjacency established.
g. Use the show ip ospf neighbor detail command to get additional information about neighbor adjacencies.
R3# show ip ospf neighbor detail Neighbor 2.2.2.1, interface address 172.16.1.1 In the area 0 via interface GigabitEthernet0/1 Neighbor priority is 1, State is FULL, 6 state changes DR is 172.16.1.1 BDR is 172.16.1.2 Options is 0x12 in Hello (E-bit, L-bit) Options is 0x52 in DBD (E-bit, L-bit, O-bit) LLS Options is 0x1 (LR) Dead timer due in 00:00:37 Neighbor is up for 00:21:50 Index 1/1/1, retransmission queue length 0, number of retransmission 0 First 0x0(0)/0x0(0)/0x0(0) Next 0x0(0)/0x0(0)/0x0(0) Last retransmission scan length is 0, maximum is 0 Last retransmission scan time is 0 msec, maximum is 0 msec |
As shown, the output confirms various information about the OSPF neighbor including DR and BDR status.
h. Verify the OSPF routes in the routing table using the show ip route ospf command.
R3# show ip route ospf | begin Gateway Gateway of last resort is 172.16.1.1 to network 0.0.0.0
O*E2 0.0.0.0/0 [110/1] via 172.16.1.1, 00:26:08, GigabitEthernet0/1 10.0.0.0/8 is variably subnetted, 4 subnets, 3 masks O IA 10.10.0.0/30 [110/30] via 172.16.1.1, 00:26:08, GigabitEthernet0/1 O IA 10.10.1.0/24 [110/40] via 172.16.1.1, 00:26:08, GigabitEthernet0/1 172.16.0.0/16 is variably subnetted, 3 subnets, 2 masks O 172.16.0.0/30 [110/20] via 172.16.1.1, 00:26:08, GigabitEthernet0/1 |
The output verifies that R3 has received a default route from R2, two interarea routes (i.e., O IA routes) and one intra-area OSPF route (i.e., O routes). The O*E2 route indicates that this is an external route that did not originate in OSPF. The asterisk identifies this as a candidate default route.
i. Now get detailed information on how R3 learned about the O E2 and O IA routes.
R3# show ip route 0.0.0.0 Routing entry for 0.0.0.0/0, supernet Known via “ospf 123“, distance 110, metric 1, candidate default path Tag 123, type extern 2, forward metric 1 Last update from 172.16.1.1 on GigabitEthernet0/1, 00:28:41 ago Routing Descriptor Blocks: * 172.16.1.1, from 2.2.2.1, 00:28:41 ago, via GigabitEthernet0/1 Route metric is 1, traffic share count is 1 Route tag 123 |
R3# show ip route 10.10.1.0 Routing entry for 10.10.1.0/24 Known via “ospf 123“, distance 110, metric 13, type inter area Last update from 172.16.1.1 on GigabitEthernet0/1, 00:29:10 ago Routing Descriptor Blocks: * 172.16.1.1, from 1.1.1.1, 00:29:10 ago, via GigabitEthernet0/1 Route metric is 13, traffic share count is 1 |
The output confirms that R3 learned about the default route from R2 (2.2.2.1) and interarea routes from R1 (1.1.1.1) via OSPF.
Last to configure is D2. Like D1, D2 is an internal router in Area 2.
a. Layer 3 switches are not enabled to perform routing by default. Therefore, routing must be enabled using the ip routing global configuration command.
Open configuration window
| D2(config)# ip routing |
b. Next, enter the OSPF router configuration mode using process ID 123, assign the D2 the router ID 3.3.3.2, and set the reference bandwidth to distinguish between Gigabit Ethernet and FastEthernet interfaces.
D2(config)# router ospf 123 D2(config-router)# router-id 3.3.3.2 D2(config-router)# auto-cost reference-bandwidth 10000 % OSPF: Reference bandwidth is changed. Please ensure reference bandwidth is consistent across all routers. |
c. Configure D2 to advertise its interfaces in OSPF Area 2 and return to privileged EXEC mode.
D2(config-router)# network 10.10.4.0 0.0.0.3 area 2 D2(config-router)# network 10.10.5.0 0.0.0.255 area 2 D2(config-router)# end D2# *Mar 1 01:52:03.888: %OSPF-5-ADJCHG: Process 123, Nbr 3.3.3.1 on GigabitEthernet0/2 from LOADING to FULL, Loading Done |
d. Verify the OSPF configuration on D2 using the show ip protocols command.
D2# show ip protocols Routing Protocol is “ospf 123” Outgoing update filter list for all interfaces is not set Incoming update filter list for all interfaces is not set Router ID 3.3.3.2 Number of areas in this router is 1. 1 normal 0 stub 0 nssa Maximum path: 4 Routing for Networks: 10.10.4.0 0.0.0.3 area 2 10.10.5.0 0.0.0.255 area 2 Routing Information Sources: Gateway Distance Last Update 3.3.3.1 110 00:09:35 2.2.2.1 110 00:04:38 Distance: (default is 110) |
As expected, we can verify the router ID, number of areas, networks being advertised, and routing sources. It may be surprising that R2 (i.e., 2.2.2.1) is displayed as a routing source. The reason is because it is the source of the default route.
e. Verify that the reference bandwidth has been changed using the show ip ospf | begin Ref command as shown.
D2# show ip ospf | begin Ref Reference bandwidth unit is 10000 mbps Area 2 Number of interfaces in this area is 2 Area has no authentication SPF algorithm last executed 00:13:01.877 ago SPF algorithm executed 3 times <output omitted> |
f. Verify the active OSPF interfaces and assigned areas using the show ip ospf interface brief command.
D2# show ip ospf interface brief Interface PID Area IP Address/Mask Cost State Nbrs F/C Gi0/3 123 2 10.10.5.1/24 10 DR 0/0 G10/2 123 2 10.10.4.2/30 1 BDR 1/1 |
The output confirms that the two interfaces are in Area 2 and their IP addresses are correct.
g. Verify which OSPF neighbors D2 has established an adjacency with using the show ip ospf neighbor command.
D2# show ip ospf neighbor Neighbor ID Pri State Dead Time Address Interface 3.3.3.1 1 FULL/BDR 00:00:33 10.10.4.1 GigabitEthernet0/2 |
The output confirms that D2 has one neighbor (i.e., 3.3.3.1= R3) and they have a full adjacency established.
h. Verify the OSPF routes in the routing table using the show ip route ospf | begin Gateway command.
D2# show ip route ospf | begin Gateway Gateway of last resort is 10.10.4.1 to network 0.0.0.0
O*E2 0.0.0.0/0 [110/1] via 10.10.4.1, 00:09:25, Gigabitthernet0/2 10.0.0.0/8 is variably subnetted, 6 subnets, 3 masks O IA 10.10.0.0/30 [110/40] via 10.10.4.1, 00:09:00, GigabitEthernet0/2 O IA 10.10.1.0/24 [110/50] via 10.10.4.1, 00:09:00, GigabitEthernet0/2 172.16.0.0/30 is subnetted, 2 subnets O IA 172.16.0.0 [110/30] via 10.10.4.1, 00:09:00, GigabitEthernet0/2 O IA 172.16.1.0 [110/20] via 10.10.4.1, 00:09:00, GigabitEthernet0/2 |
The output displays four interarea routes (i.e., O IA routes) and the OSPF external route from 2.2.2.1(R2).
D2# show ip route 0.0.0.0 Routing entry for 0.0.0.0/0, supernet Known via “ospf 123”, distance 110, metric 1, candidate default path Tag 123, type extern 2, forward metric 2 Last update from 10.10.4.1 on GigabitEthernet0/2, 00:18:31 ago Routing Descriptor Blocks: * 10.10.4.1, from 2.2.2.1, 00:18:31 ago, via GigabitEthernet0/2 Route metric is 1, traffic share count is 1 Route tag 123 |
As we can see, the routing source for the default route is R2 (i.e., 2.2.2.1).
The multiarea OSPF network is now completely configured. We now need to verify the operation of OSPF.
a. From PC1, verify that it has been assigned the correct IP address as listed in the Addressing Table using the ipconfig Windows command.
C:\Users\Student> ipconfig
Windows IP Configuration
Ethernet adapter Ethernet0:
Connection-specific DNS Suffix . : Link-local IPv6 Address . . . . . : fe80::7853:120b:ecdf:d718%6 IPv4 Address. . . . . . . . . . . : 10.10.1.10 Subnet Mask . . . . . . . . . . . : 255.255.255.0 Default Gateway . . . . . . . . . : 10.10.1.1 |
b. Verify end-to-end connectivity by pinging PC3.
C:\Users\Student> ping 10.10.5.10
Pinging 10.10.5.10 with 32 bytes of data:
Pinging 10.10.5.10 with 32 bytes of data: Reply from 10.10.5.10: bytes=32 time=1ms TTL=123 Reply from 10.10.5.10: bytes=32 time=1ms TTL=123 Reply from 10.10.5.10: bytes=32 time=1ms TTL=123 Reply from 10.10.5.10: bytes=32 time=1ms TTL=123
Ping statistics for 10.10.5.10: Packets: Sent = 4, Received = 4, Lost = 0 (0% loss), Approximate round trip times in milli-seconds: Minimum = 0ms, Maximum = 1ms, Average = 0ms |
c. Verify the route taken by doing a traceroute to PC3.
C:\Users\Student> tracert 10.10.5.10 Tracing route to DESKTOP-3FR7RKA [10.10.5.10] over a maximum of 30 hops:
1 1 ms 1 ms 1 ms 10.10.1.1 2 <1 ms <1 ms <1 ms 10.10.0.1 3 1 ms <1 ms <1 ms 172.16.0.1 4 1 ms 1 ms <1 ms 172.16.1.2 5 1 ms 2 ms 2 ms 10.10.4.2 6 1 ms <1 ms <1 ms DESKTOP-3RF7RKA [10.10.5.10] |
Trace complete.
This confirms end-to-end connectivity.
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