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IP Routing Protocols by Uyless Black

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The OSPF Packets

Figure 6-16 illustrates the 20-octet OSPF packet header. Each OSPF LSA packet is appended with this header. The fields in the header mean the following. I provide a general description here, and the many rules and details for this packet are available in the OSPF RFC.

Figure 6-16. The Link State Advertisement (LSA) Header

The LS Age field shows the number of seconds from the origination of the LSA. Typically, it ranges from 0 to 30 minutes, and if the age exceeds 30 minutes, the originating router resends the LSA, and sets this field to 0 (as well as incrementing the LS Sequence Number).

The Options field is used to indicate that ...

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