This tutorial will show you how you can configure stub and NSSA OSPF areas. Before you jump and start configuring them, I advise you to go over these two articles from Intense School website: OSPF Areas – Part I and OSPF Areas – Part II.

These two articles will give you a refresh on OSPF area types.

For this simulation I created two Packet Tracer files:

  • configuring_ospf_areas_init.pkt – this is the starting point of the exercise. The IP addressing is configured and only area 0 is configured
  • configuring_ospf_areas_final.pkt – this is the result of the exercise. Use this file to compare your configuration and see if you did everything correctly

Regarding the topology, each router has a loopback address in the form of 1.1.1.X/32, where X is the router number. For instance, the loopback address of R8 is 1.1.1.8/32.

The loopback interfaces should be configured in the following areas:

  1. R1 – area 0
  2. R2 – area 0
  3. R3 – area 0
  4. R4 – area 0
  5. R5 – area 3
  6. R6 – area 1
  7. R7 – area 4
  8. R8 – area 2

Also, each subnet between the routers is written on the topology and every router is using as the last octet its router number. For instance, on the subnet 10.10.14.0/24, R1 has 10.10.14.1/24 and R4 has 10.10.14.4/24.

There are five OSPF areas on the diagram.

R1, R2, R3 and R4 are backbone routers, hence they are part of area 0 and all these four routers are configured for area 0.

The other four areas will be configured as following:

  1. area 1 – stub area
  2. area 2 – totally stub area
  3. area 3 – NSSA
  4. area 4 – totally NSSA

Task 1 requirements

  1. on R1 configure the interface GigabitEthernet0/2 to be part of the area 1
  2. On R1 configure area 1 to be stub area
  3. On R6 configure the interface GigabitEthernet0/0 to be part of the area 1
  4. On R6 configure the interface Loopback0 to be part of the area 1
  5. On R6 configure area 1 to be stub area

Task 1 verification

  1. On R6, issue the command ‘show ip ospf neighbor’ to confirm that the OSPF adjacency with R1 is up. Your output should be similar to this one:

    R6#show ip ospf neighbor
    Neighbor ID Pri State Dead Time Address Interface
    1.1.1.1 1 FULL/DR 00:00:39 10.10.16.1 GigabitEthernet0/0
    R6#

  2. On R6, issue the command ‘show ip ospf’ to confirm that area 1 is stub area.

Task 1 hints

  1. On R1 use the command ‘network 10.10.16.1 0.0.0.0 area 1’ to put g0/2 in area 1
  2. On R1 use the command ‘area 1 stub’ to configure area 1 as stub area
  3. On R6 use the command ‘network 10.10.16.6 0.0.0.0 area 1’ to put g0/0 in area 1
  4. On R6 use the command ‘network 1.1.1.6 0.0.0.0 area 1’ to put lo0 in area 1
  5. On R6 use the command ‘area 1 stub’ to configure area 1 as stub area

Task 2 requirements

  1. on R4 configure the interface GigabitEthernet0/2 to be part of the area 2
  2. On R4 configure area 2 to be totally stub area
  3. On R8 configure the interface GigabitEthernet0/0 to be part of the area 2
  4. On R8 configure the interface Loopback0 to be part of the area 2
  5. On R8 configure area 2 to be totally stub area

Task 2 verification

  1. On R8, issue the command ‘show ip ospf neighbor’ to confirm that the OSPF adjacency with R4 is up. Your output should be similar to this one

    R8#show ip ospf neighbor
    Neighbor ID Pri State Dead Time Address Interface
    1.1.1.4 1 FULL/BDR 00:00:31 10.10.48.4 GigabitEthernet0/0
    R8#

  2. On R8, use the command ‘show ip ospf database’ to confirm that the only LSA type 3 is the one for default route. Your output should be similar to this one:

    Summary Net Link States (Area 2)
    Link ID ADV Router Age Seq# Checksum|
    0.0.0.0 1.1.1.4 890 0x8000000b 0x004ffd
    R8#

Task 2 hints

  1. On R4 use the command ‘network 10.10.48.4 0.0.0.0 area 2’ to put g0/2 in area 1
  2. On R4 use the command ‘area 2 stub no-summary’ to configure area 2 as totally stub area
  3. On R8 use the command ‘network 10.10.48.8 0.0.0.0 area 2’ to put g0/0 in area 1
  4. On R8 use the command ‘network 1.1.1.8 0.0.0.0 area 1’ to put lo0 in area 2
  5. On R8 use the command ‘area 2 stub’ to configure area 2 as totally stub area

Task 3 requirements

  1. on R2 configure the interface GigabitEthernet0/0 to be part of the area 3
  2. On R2 configure area 3 to be NSSA area
  3. On R5 configure the interface GigabitEthernet0/0 to be part of the area 3
  4. On R5 configure the interface Loopback0 to be part of the area 3
  5. On R5 configure area 3 to be NSSA area

Task 3 verification

  1. On R5, issue the command ‘show ip ospf neighbor’ to confirm that the OSPF adjacency with R2 is up. Your output should be similar to this one:

    R5#sh ip ospf neighbor
    Neighbor ID Pri State Dead Time Address Interface
    1.1.1.2 1 FULL/DR 00:00:33 10.10.25.2 GigabitEthernet0/0
    R5#

  2. On R5, issue the command ‘show ip ospf’ to confirm that area 5 is NSSA area

Task 3 hints

  1. On R2 use the command ‘network 10.10.25.2 0.0.0.0 area 3’ to put g0/0 in area 3
  2. On R2 use the command ‘area 3 nssa’ to configure area 3 as NSSA area
  3. On R5 use the command ‘network 10.10.25.5 0.0.0.0 area 3’ to put g0/0 in area 3
  4. On R5 use the command ‘network 1.1.1.5 0.0.0.0 area 3’ to put lo0 in area 3
  5. On R5 use the command ‘area 3 nssa’ to configure area 3 as NSSA area

Task 4 requirements

  1. on R3 configure the interface GigabitEthernet0/2 to be part of the area 4
  2. On R3 configure area 4 to be totally NSSA area
  3. On R7 configure the interface GigabitEthernet0/0 to be part of the area 4
  4. On R7 configure the interface Loopback0 to be part of the area 4
  5. On R7 configure area 4 to be totally NSSA area

Task 4 verification

  1. On R7, issue the command ‘show ip ospf neighbor’ to confirm that the OSPF adjacency with R3 is up. Your output should be similar to this one:

    R7#show ip ospf neighbor
    Neighbor ID Pri State Dead Time Address Interface
    1.1.1.3 1 FULL/DR 00:00:37 10.10.37.3 GigabitEthernet0/0
    R7#

  2. On R7, use the command ‘show ip ospf database’ to confirm that the only LSA type 3 is the one for default route. Your output should be similar to this one:

    Summary Net Link States (Area 4)
    Link ID ADV Router Age Seq# Checksum
    0.0.0.0 1.1.1.3 835 0x8000000f 0x004dfc
    R7#

Task 4 hints

  1. On R3 use the command ‘network 10.10.37.3 0.0.0.0 area 4’ to put g0/2 in area 4
  2. On R3 use the command ‘area 4 nssa no-summary’ to configure area 4 as totally NSSA area
  3. On R7 use the command ‘network 10.10.37.7 0.0.0.0 area 4’ to put g0/0 in area 4
  4. On R7 use the command ‘network 1.1.1.7 0.0.0.0 area 4’ to put lo0 in area 4
  5. On R7 use the command ‘area 4 nssa’ to configure area 4 as totally NSSA area

As you can see, there are specific knobs that needs to be used when different OSPF areas have to be configured.

With OSPF areas, the hardest part is to understand what’s the difference between them. All comes down to have a good understanding of them. It’s more important to understand why do you need a specific OSPF area and not another one.

Basically, this is almost everything that you can experiment with OSPF areas using Packet Tracer.