3Com Switch 4800G 24-Port Configuration Manual page 284

284 C 28: OSPF C
HAPTER ONFIGURATION
Figure 82 Hello packet format
0
Version
HelloInterval
Major fields:
Network Mask: Network mask associated with the router's sending interface. If
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two routers have different network masks, they cannot become neighbors.
HelloInterval: Interval for sending hello packets. If two routers have different
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intervals, they cannot become neighbors.
Rtr Pri: Router priority. A value of 0 means the router cannot become the
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DR/BDR.
RouterDeadInterval: Time before declaring a silent router down. If two routers
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have different time values, they cannot become neighbors.
Designated Router: IP address of the DR interface.
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Backup Designated Router: IP address of the BDR interface
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Neighbor: Router ID of the neighbor router.
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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:
7 15
1
Router ID
Area ID
Checksum
Authentication
Authentication
Network Mask
RouterDeadInterval
Designated router
Backup designated router
Neighbor
Neighbor
Packet length
AuType
Options Rtr Pri
31