Can someone please explain to me Why I do have 9 LSA type 3 on Router B and D in this topology ? enter image description here

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1 Answer 1


Both router B and D are your ABRs (area border routers), which hold summaries for the areas they border, in your case they hold summaries for areas 1 and 0, and 0 and 2 respectively. Type 3 LSA's are summary LSA's, which if you look at both routers A and E, they already have part of the answer for you; they both have "5" LSA type 3 summaries. Then if you look at router C in area 0, it has a total of "4" type 3 LSA's. Add these summaries up, "5" + "4", on each ABR, you have your "9" type 3 LSAs.

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