Working from the my last couple of OSPF posts I am going to try and crystallize some of the material found by working through questions found in Stewart, B,D., Gough, C (2008). CCNP BSCI Official Exam Certification Guide, Fourth Edition. Indianapolis: Cisco Press book.
11. what is the sequence number and where is it held?
The sequence number is a field with numbers so that older and/or newer versions of LSA advertisements can be recognized from each other (start 0×8000 0001 end 0xFFFF FFFF before rolling to the start again). The eventual goal is that all routers in the same AS has the same LSDB which is then processed using SPF from which the best routes are selected and a routing table created.
The sequence number is held within the Topology Database.
Notes and Notices: This is a part of my personal BSCI notes and research to assist myself in learning and understanding the concepts and theory for the BSCI exam. I learn by making notes reading and writing things down and wish to file them where I cannot lose them. These notes are not to be seen, judged or mistaken for replacements to Cisco recognized and authorized training which I personally support and attend and suggest you undertake if you are going for the BSCI Certification.