The mandatory information within the Hello update that must match exactly are the hello and dead timer values intervals, area ID, OSPF area type, subnet, and authentication data if used. If any of those don't match perfectly, no adjacency will occur!
- Chapter 20: Multi-Area OSPF
- from CCNA Routing and Switching Deluxe Study Guide: Exams 100-101, 200-101, and 200-120
- Publisher: Sybex
- Released: December 2013
Mental note needed