Categories of LSAs
In the discussion of link-state protocols, you read that every router advertises its active OSPF links to all its neighbors; you also learned about the five categories of links that the router advertises in OSPF. Recall that the five link states are:
| Type | Description |
|---|---|
| 1 | Router link state |
| 2 | Network link state |
| 3 | Summary link state (type 3) |
| 4 | Summary link state (type 4) |
| 5 | External link state |
All link states share a common LSA header because every link state must advertise some common information. Figure 9-7 shows the common 20-byte LSA header that is shared by all types of LSAs.
Figure 9-7. Common 20-Byte LSA Header
The common LSA header contains the following information:
LS age This is the time in seconds since ...
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