OSPF Stub Area and Totally-Stub Area on Cisco Packet Tracer

In the previous OSPF (Open Shortest Path First) lessons we had talked about standard Standard and Backbone area types. In this lesson, we will talk about two of the the other Area Types of OSPF. Here, we will learn OSPF Stub Area Configuration and Totally Stub Area Configuration.

In this Open Shortest Path First lesson we will focus on configuration mostly. But firstly, let’s talk about the theorical part of this OSPF Stub Area lesson.

You can DOWNLOAD the Packet Tracer example with .pkt format at the end of this lesson.

You can check the below lessons for the configuration of different OSPF Area Types:

• Multi Area OSPF Configuration
• Stub Area & Totally-Stub Area Configuration
• NSSA and Totally NSSA Configuration
• External OSPF Routes

Stub Areas, Totally-Stub Areas, Not So Stubby Areas and Totally Not So Stubby Areas are the other area types of OSPF. These area types are prevent some routes to enter the Area routers. We will check all of these one by one.

For this article, the below topology will be our reference topology.

OSPF Area Types Example Topology

What is Stub Area? OSPF Stub Area Configuration

OSPF Stub Area is the area that do not accept the External LSAs(Type 5). Stub Areas accept the summary LSAs Type 3 beside the Default Route from the Backbone Area. They also do not accept Type 4 LSAs.

To configure an area as a Stub Area, we need to configure all the routers in this area as Stub. Because, configuring a router interface as a Stub, changes the option bits in the Hello Packets. To form a new neigbourship, the other end router need to be configured as Stub.

The OSPF Stub Area Cofiguration is like below:

router ospf 1
area 10 stub

On our main topology, we will configure the Area 1 as stub. The stub area configuration will be like below on both Router1 and Router3:

Router1(config)# router ospf 1
Router1(config-router)# area 1 stub

Router3(config)# router ospf 1
Router3(config-router)# area 1 stub

After this configuration, the show ip route output will be like below:

Router3#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 10.2.0.1 to network 0.0.0.0

     10.0.0.0/8 is variably subnetted, 7 subnets, 2 masks
O IA    10.1.0.0/24 [110/2] via 10.2.0.1, 00:00:38, GigabitEthernet0/1
C       10.2.0.0/24 is directly connected, GigabitEthernet0/1
L       10.2.0.2/32 is directly connected, GigabitEthernet0/1
O IA    10.3.0.0/24 [110/3] via 10.2.0.1, 00:00:28, GigabitEthernet0/1
O IA    10.4.0.0/24 [110/4] via 10.2.0.1, 00:00:18, GigabitEthernet0/1
O IA    10.6.0.0/24 [110/2] via 10.2.0.1, 00:00:38, GigabitEthernet0/1
O IA    10.7.0.0/24 [110/3] via 10.2.0.1, 00:00:28, GigabitEthernet0/1
O*IA 0.0.0.0/0 [110/2] via 10.2.0.1, 00:00:38, GigabitEthernet0/1

As you can see, Type 3, Type 4 LSAs and Default Route is in the routing table. External LSAs, Type 5 is not accepted.

What is Totally-Stub Area? OSPF Totally-Stub Area Configuration

In OSPF Totally- Stub Area, beside External LSAs (Type 5), LSAs Type 3 and Type 4 are also not accepted. Only a default-route is accepted by a Totally-Stub Area.

To configure an area as Totally-Stub, you need to configure only the ABR of that area. Configuring an area as Totally-Stub do not affect the Hello packets. So all the routers do not need to be configured for totatly-stub in the area.

OSPF Totally- Stub Configuration will be like below:

router ospf 1
area 10 stub no-summary

On our main topology, we will configure the Area 3 as totally stubby area. The totally stubby area configuration will be like below on both Router7 and Router1:

Router7(config)# router ospf 1
Router7(config-router)# area 3 stub no-summary

Router1(config)# router ospf 1
Router1(config-router)# area 3 stub no-summary

After this configuration, the show ip route output will be like below:

Router7#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 10.6.0.1 to network 0.0.0.0

     10.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
C       10.6.0.0/24 is directly connected, GigabitEthernet0/2
L       10.6.0.2/32 is directly connected, GigabitEthernet0/2
O*IA 0.0.0.0/0 [110/2] via 10.6.0.1, 00:14:26, GigabitEthernet0/2

As you can see above output, there is only one default route on routing table. There is no Type3, Type 4 and Type 5 LSAs.

In the next lesson, we will talk about the other Open Shortest Path First Areas.

You can DOWNLOAD the Packet Tracer example with .pkt format HERE.

You can download “Cisco Packet Tracer” in Tools section.

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