HP 4800G Series Configuration Manual page 446

Figure 1-10 Hello packet format
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HelloInterval
Major fields:
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/BDR.
RouterDeadInterval: Time before declaring a silent router down. If two routers have different time
values, they cannot become neighbors.
Designated router: IP address of the DR interface.
Backup designated router: IP address of the BDR interface
Neighbor: Router ID of the neighbor router.
DD packet
Two routers exchange database description (DD) packets describing their LSDBs for database
synchronization, contents in DD packets including the header of each LSA (uniquely representing a
LSA). The LSA header occupies small part of an LSA to reduce traffic between routers. The recipient
checks whether the LSA is available using the LSA header.
The DD packet format:
15
1
Router ID
Area ID
Authentication
Authentication
Network mask
Options
RouterDeadInterval
Designated router
Backup designated router
Neighbor
Neighbor
1-11
Packet length
AuType
Rtr Pri
31