A link is any type of connection between OSPF routers, such as a frame relay link or an Ethernet segment. The state is the condition of the link, that is, whether the link is available for use (for example, up or down). An advertisement is the method that OSPF uses to provide information to other OSPF routers. Therefore, LSAs are a special type of packet that OSPF uses to advertise changes in the state of a specific link to other OSPF routers.
Types of LSAs
Unlike distance vector protocols (RIP or IGRP), OSPF does not send its routing table to other routers. Instead, routing tables are derived from the LSA database, as discussed in Chapter 2. OSPF has a variety of router designations and area types. This complexity ...