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DES-3326S Layer 3 Fast Ethernet Switch User’s Guide
140 Switch Management and Operating Concepts
• Loading − 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outdated will be put on the request list.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.
• Full − 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.
• OSPF packet header
• Hello packet
• Database Description packet
• Link-State Request packet
• The Link-State Update packet
• Link-State Acknowledgment packet