I see no topic on ospf demand circuit. Could you please guide me on it.
It is true that there is no lesson about this specific topic. However, you can find some info about it and a related lab at the following GNS3Vault link:
Now if you want to suggest that this topic be included in the NetworkLessons site, feel free to visit the Member Ideas page and make a suggestion. You may find that others have made similar suggestions, and you can add your voice to theirs.
I hope this has been helpful!
Thanks for the support