The Cisco admin guide to remembering OSPF details

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Added by Mark Jacob April 22, 2013

If you have read my previous blogs, you know that I am a big fan of memory aids. Since the human brain is typically not gifted at simply storing vast amounts of information, I want to give myself, and you the reader, as much help as possible in remembering stuff.

One of my memory aid deals with remembering the Hello timers (and Dead timers – usually four times the Hello value) on various types of Open Shortest Path First (OSPF) networks. Here is a table with the information:

Notice the funny-looking Ms. They look like the letter 3 turned on its side. Guess what! They are supposed to. Each of the network types that has an ‘M’ in it also has a Hello time of 30 seconds. Sweet, eh?

I have one more you might like. Using the same network types as above, let me modify the table slightly:

You notice that the ones with the bold ‘non’ do not discover neighbors automatically. My key is ‘non’ equals ‘no neighbors.’

These are just a couple of the memory aids I use to help me keep track of the nitty gritty details involved with the OSPF routing protocol. If you have others, please feel free to share your comments.

Until next time…

Mark Jacob
Cisco Instructor – Interface Technical Training
Phoenix, AZ