cisco packet tracer representation topology example

Each router builds a link-state packet (LSP)containing the state of each directly connected link.

Link-state routers do this by exchanging Hello packets with other link-state routers on directly connected networks.

Each router is responsible for meeting its neighbors on directly connected networks.This is done by detecting that an interface is in the up state. Each router learns about its own links and its own directly connected networks.Information about the state of those links is known as link-states.Īll routers in an OSPF area will complete the following generic link-state routing process to reach a state of convergence: So exactly how does a link-state routing protocol work? With link-state routing protocols, a link is an interface on a router. This section discusses how OSPF exchanges LSUs to discover the best routes. Link-state updates (LSUs) are the packets used for OSPF routing updates. Observe the shortest path for each router to reach each of the LANs, as shown in Tables 3-8 through 3-11.

However, the cost to reach R4 directly (22) is higher than the cost to reach R4 through R3 (17). It might be assumed that R1 would send directly to R4 instead of to R3.

For example, look at the path to the R5 LAN. The shortest path is not necessarily the path with the least number of hops. Intermediate System-to-Intermediate System (IS-IS) The IPv4 link-state routing protocols are shown Figure 3-35: The SPF algorithm is discussed in more detail in a later section. Link-state routing protocols are also known as shortest path first protocols and are built around Edsger Dijkstra’s shortest path first (SPF) algorithm. Understanding the operation of link-state routing is critical to enabling, verifying, and troubleshooting these protocols. This section describes the characteristics, operations, and functionality of link-state routing protocols. Link-State Routing Protocol Operation (3.4.1) In many ways, the link-state process is simpler to understand than distance vector concepts. However, link-state routing protocols and concepts are not difficult to understand. Distance vector routing protocols are thought to be simple to understand, whereas link-state routing protocols have the reputation of being very complex, even intimidating.

Cisco packet tracer representation topology example