H3C S5800 Series Configuration Manual page 86

MD5 authentication data is added following an OSPF packet rather than contained in the
Authentication field.
Hello packet
A router sends hello packets periodically to neighbors to find and maintain neighbor relationships and
to elect the DR/BDR, including information about values of timers, DR, BDR and neighbors already
known. The format is shown below:
Figure 4-10 Hello packet format
0
Version
Checksum
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
7 15
1
Router ID
Area ID
Authentication
Authentication
Network mask
RouterDeadInterval
Designated router
Backup designated router
Neighbor
Neighbor
Packet length
AuType
Options
4-11
31
Rtr Pri