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Figure 26
Hello packet format
...
Major fields of the hello packet are as follows:
•
Network mask: Network mask associated with the router’s sending interface. If two routers have
different network masks, they cannot become neighbors.
•
HelloInterval: Interval for sending hello packets. If two routers have different intervals, they cannot
become neighbors.
•
Rtr Pri: Router priority. A value of 0 means the router cannot become the DR or BDR.
•
RouterDeadInterval: Time before declaring a silent router down. If two routers have different dead
intervals, they cannot become neighbors.
•
Designated router: IP address of the DR.
•
Backup designated router: IP address of the BDR.
•
Neighbor: Router ID of the neighbor router.
DD packet
Two routers exchange database description (DD) packets, describing their LSDBs for database
synchronization. A DD packet contains only the headers of LSAs to reduce traffic.
