H3C S3610-28P Operation Manual page 381

Operation Manual – IPv4 Routing
H3C S3610&S5510 Series Ethernet Switches
II. 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:
0
Version
Figure 3-10 Hello packet format
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.
III. 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
7
1
Checksum
HelloInterval
RouterDeadInterval
Designated router
Backup designated router
3-13
15
Packet length
Router ID
Area ID
Authentication
Authentication
Network Mask
Options
Neighbor
Neighbor
Chapter 3 OSPF Configuration
AuType
Rtr Pri
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