63
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.
...
Network mask
HelloInterval
Options
Rtr Pri
RouterDeadInterval
Designated router
Backup designated router
Neighbor
Version
1
Router ID
Area ID
Checksum
AuType
Packet length
Authentication
Authentication
0
7
15
31
Neighbor
