How to Read the OSPF Database Lesson

Routing & Switching OSPF
1

I believe I found an error in the document “How to Read the OSPF Database”. On R1 you run:
#show ip ospf database network 10.0.34.3
The following diagram does not show an edge (link) between R5 and DR.
Next you run:
#show ip ospf database router 5.5.5.5
and you show an edge (link) between R5 and DR
with 15.0/24, cost 17.
I believe this link should not be there. There are 2 point to point connections 15.5 to R1 and 35.5 to R3, so 15.0/24, cost 17 should be drawn as a stub network like 5.0/24, cost 30 and 35.0/24, cost 17 that you have indicated on R5.
pic2

I have circled the edge link in red and also inserted a stub link for the 15.0/24, cost 17 indicating the changes I think should be made.

So I believe all of diagrams should remove the edge (link) to the DR.

Is this correct? I’m using my home lab to work through your document to increase my understanding of how to read the OSPF database.

Thanks in advance,

Evan Fareed

2

Hello Evan F

Yes you are correct. For the specific link, the output of the show ip ospf database router 5.5.5.5 command on R5 shows the following:

Link connected to: a Stub Network
 (Link ID) Network/subnet number: 10.0.15.0
 (Link Data) Network Mask: 255.255.255.0
  Number of TOS metrics: 0
   TOS 0 Metrics: 17

So this is a STUB and it should be indicated as you have it on your diagram.

I’m not sure if the output is stated incorrectly in the lesson or if the diagram itself must be changed. In any case, I will let @ReneMolenaar know about this error.

Thanks very much!

Laz