DGS-3312SR Stackable Gigabit Layer 3 Switch
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The routers are finalizing the information exchange. Routers have link-state request list and a
link-state retransmission list. Any information that looks incomplete or outdated will be put on the
request list. Any update that is sent will be put on the retransmission list until it gets acknowledged.
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Full
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The adjacency is now complete. The neighboring routers are fully adjacent. Adjacent routers will
have the same link-state database.
Adjacencies on Point-to-Point Interfaces
OSPF Routers that are linked using point-to-point interfaces (such as serial links) will always form adjacencies. The
concepts of DR and BDR are unnecessary.
OSPF Packet Formats
All OSPF packet types begin with a standard 24-byte header and there are five packet types. The header is described first,
and each packet type is described in a subsequent section.
All OSPF packets (except for Hello packets) forward link-state advertisements. Link-State Update packets, for example,
flood advertisements throughout the OSPF routing domain.
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OSPF packet header
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Hello packet
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Database Description packet
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Link-State Request packet
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The Link-State Update packet
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Link-State Acknowledgment packet
OSPF Packet Header
Every OSPF packet is preceded by a common 24-byte header. This header contains the information necessary for a
receiving router to determine if the packet should be accepted for further processing.
The format of the OSPP packet header is shown below:
OSPF Packet Header
Type
Packet Length
Router ID
Area ID
Checksum
Authentication Type
Authentication
Authentication
Version No.
Figure 5- 19. OSPF Packet Header
Field Description
Version No.
The OSPF version number
Type
The OSPF packet type. The OSPF packet types are as follows:
Type Description
Hello
Database Description