How to configure OSPF Stub Area

ah don’t do that Rene you already are very responsive and take care of the website. Save your time for important stuff it was small inconvenience only I just glossed over the names and focused on specific granular that I was having problems with but makes me feel bad if you try to do something that difficult in the time consuming meticulous area.

I think its fine. I saw in another post once where someone griped about named routers and maybe some truth but then you said you might change it then you went back and fixed it. That had repercussion of making some of the forums post be off no biggie you was just being too helpful lol! I would not worry about changing all past things unless its something that is easy and efficient just use new method going forward.

You are to important to all of us to be spending your time trying to read through things you have already worked on in the past and only a limited number of the hardcore study people will read through.

Your website is already the best out there for content, and for team that is responsive to replying and helping. I am a professional student as I love to learn I would not pull your leg or inflate your ego.

This is hands down the best networking site with content and forums. Not many people with your knowledge and ability would do what you do to the level you do it. Oh and lets give credit to those moderators as well like Las and Andrew. Great team!

Hands down the most cost efficient way to learn about Cisco Networking this site is worth double or triple what you charge but I am thankful you give the people such a great deal. I am a happy person by nature but I am also a very honest person and I am not a person that believes in being inefficient and wasting my time talking up their company because I like them or was just being nice. No that’s all truth.

I think we will all live =)

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Yes that is helpful I do understand your diagram. Thanks!

Hi Rene,
That was mind blowing. Clear concept indeed . The stub/Totally Stub concerned to how many exit point from a area .The NSSA/Totally NSSA needed when ASBR needed on a area .Thx


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Hi Rene,
I am trying to replicate the same scenario in lab, but the loopback network is not being redistributed.
on R1:

interface Loopback0
 ip address
interface FastEthernet0/0
 ip address
 duplex auto
 speed auto
router ospf 1
 redistribute connected subnets
 network area 0

Could you please guide as to what i am missing?

Hi Rajani,

Your config looks OK. You do have a working neighbor adjacency between R1 and the other router?

You can also verify that it’s in the LSDB of R1:

R1#show ip ospf database external 

            OSPF Router with ID ( (Process ID 1)

                Type-5 AS External Link States

  LS age: 1127
  Options: (No TOS-capability, DC, Upward)
  LS Type: AS External Link
  Link State ID: (External Network Number )
  Advertising Router:
  LS Seq Number: 80000001
  Checksum: 0xA5F3
  Length: 36
  Network Mask: /24
        Metric Type: 2 (Larger than any link state path)
        MTID: 0 
        Metric: 20 
        Forward Address:
        External Route Tag: 0


Hi Rajini,

Looks like you have wrong IP configured on your Fa0/0 ( and distributing
you can change the interface IP address of fa0/0 and you can see the Loopback being redistributed.
hope this helps

simple question :slight_smile:

area type must match on both routers to establish an adjancency ?

Hello Juan

Yes that is correct. The area type must match in order for an adjacency to occur.


please confirm this line you want to say that like:
ABR router which is in area 1 we have configured as a totally stub area so in area 1 all stub routers which is directly connected with ABR router has an exception of LSA 3 means totally stub area rule NO TYPE 3 SUMMARY LSA will not apply in stub area so that’s why we can see IA in R3 ospf routing table

Hello Harshit

Yes your explanation sounds right. You can find out more about totally stub areas at this lesson:

I hope this has been helpful!


I understood better with this example :rofl::rofl::rofl:… thank you Rene

A post was merged into an existing topic: Introduction to OSPF Stub Areas


i have a question regarding the Stub Area:

i configured in GNS3 the same topology as yours with the 3 Routers. Then i configured on R3 on Interface 0/0 the stub area like:

router ospf 1 
area 1 stub

I intentionally did not configure interface 1/0 on R2. After that i showed the routes on R3 and saw that R3 did not have any OSPF Routes anymore. Then i configured the interface 1/0 on R2 with the area 1 stub command and suddenly on R3 i was able to see the net The was not showed anymore, as if should be like your explanation in that lesson. But i did not understood why the R3 didnt list the OSPF Routes before i configured the stub on the Interface 1/0 on R2.

Best regards,


Hello Roberto

After you configured the R3 router with Area 1 as a stub, if you were to issue the show ip ospf neighbor command, you would find that R2 and R3 were no longer neighbors. This is the reason that you saw no OSPF routes in R3 after that change.

Once you made Area 1 on R2 a stub as well, the adjacency was reestablished, and that’s why you saw the networks reappear as expected in R3.

OSPF will form neighbor adjacencies with other OSPF routers only if the area type matches. This is one of the parameters found within the hello packets that must be the same before an adjacency can be formed.

More information about this can be found here:

I hope this has been helpful!


since it’s a static route, should not be the metric = 20?

show ip route show metric to = 20.

Hello Konstantinos

The metric that OSPF chooses to use for a particular destination does not depend upon how the destination was learned. A destination network may be learned from a static route redistributed into OSPF, from a directly connected network advertised by OSPF, or from networks learned via another OSPF router. This will not affect the metric of the route.

It is the sum of the cost of outgoing interfaces along the path to the destination that determines the metric. The following shows some of the metric values assigned to particular interface speeds by default:

  • 128 Kbps | OSPF cost: 781
  • 1.544 Mbps | OSPF cost: 64
  • 10 Mbps | OSPF cost: 10
  • 100 Mbps or greater | OSPF cost: 1

This, of course, can be adjusted by changing the reference bandwidth. More about this can be found in the following lesson:

So the metric will not be affected by the fact that this particular route is statically assigned on one of the routers.

Are you possibly thinking about administrative distance? Statically defined routes have an administrative distance of 1, but only on the router they have been configured on. And why should the metric be 20? Can you elaborate?

I hope this has been helpful!