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Table Of Contents  The TCP/IP Guide
 9  TCP/IP Lower-Layer (Interface, Internet and Transport) Protocols (OSI Layers 2, 3 and 4)
      9  TCP/IP Internet Layer (OSI Network Layer) Protocols
           9  TCP/IP Routing Protocols (Gateway Protocols)
                9  TCP/IP Interior Routing Protocols (RIP, OSPF, GGP, HELLO, IGRP, EIGRP)
                     9  Open Shortest Path First (OSPF)

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OSPF General Operation and Message Types
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 Other Interior Routing Protocols
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OSPF Message Formats
(Page 3 of 7)

Database Description Message Format

These messages have a Type value of 2 in the header, and the body structure depicted in Table 128 and Figure 186.


Table 128: OSPF Database Description Message Format

Field Name

Size (bytes)

Description

Interface MTU

2

Interface MTU: The size of the largest IP message that can be sent on this router's interface without fragmentation.

Options

1

Options: Indicates which of several optional OSPF capabilities the router supports.

Flags

1

 

DD Sequence Number

4

DD Sequence Number: Used to number a sequence of Database Description messages so they are kept in order.

LSA Headers

Variable

LSA Headers: Contains link-state advertisement headers, which carry information about the LSDB. See near the end of the topic for more information on LSAs.


Figure 186: OSPF Database Description Message Format

 

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