CCNA :) Be a Good Network Administrator

Compare and contrast distance vector and link-state routing 2.1.6  This page will compare distance vector and link-state routing protocols. All distance vector protocols learn routes and then send these routes to directly connected neighbors. However, link-state routers advertise the states of their links to all other routers in the area so that each router can build a complete link-state database. These advertisements are called link-state advertisements or LSAs. Unlike distance vector routers, link-state routers can form special relationships with their neighbors and other link-state routers. This is to ensure that the LSA information is properly and efficiently exchanged. The initial flood of LSAs provides routers with the information that they need to build a link-state database. Routing updates occur only when the network changes. If there are no changes, the routing updates occur after a specific interval. If the network changes, a partial update is sent immediately. ...

Advantages and disadvantages of link-state routing 2.1.5  This page lists the advantages and disadvantages of link-state routing protocols. The following are advantages of link-state routing protocols:  Link-state protocols use cost metrics to choose paths through the network. The cost metric reflects the capacity of the links on those paths. Link-state protocols use triggered updates and LSA floods to immediately report changes in the network topology to all routers in the network. This leads to fast convergence times. Each router has a complete and synchronized picture of the network. Therefore, it is very difficult for routing loops to occur. Routers use the latest information to make the best routing decisions. The link-state database sizes can be minimized with careful network design. This leads to smaller Dijkstra calculations and faster convergence. Every router, at the very least, maps the topology of it...

Link-state routing algorithms 2.1.4  Link-state routing algorithms maintain a complex database of the network topology by exchanging link-state advertisements (LSAs) with other routers in a network. This page describes the link-state routing algorithm. Link-state routing algorithms have the following characteristics: They are known collectively as SPF protocols. They maintain a complex database of the network topology. They are based on the Dijkstra algorithm. Link-state protocols develop and maintain full knowledge of the network routers and how they interconnect. This is achieved through the exchange of LSAs with other routers in the network. Each router constructs a topological database from the LSAs that it receives. The SPF algorithm is then used to compute the reachability of destinations. This information is used to update the routing table. This process can discover changes in the network topology caused by component failure or network growt...

How routing information is maintained 2.1.3 This page will explain how link-state protocols use the following features: The LSAs A topological database The SPF algorithm The SPF tree A routing table of paths and ports to determine the best path for packets  Link-state routing protocols were designed to overcome the limitations of distance vector routing protocols. For example, distance vector protocols only exchange routing updates with immediate neighbors while link-state routing protocols exchange routing information across a much larger area. When a failure occurs in the network, such as a neighbor becomes unreachable, link-state protocols flood LSAs with a special multicast address throughout an area. This process sends information out all ports, except the port on which the information was received. Each link-state router takes a copy of the LSA and updates its link-state, or topological database. The link-state router then forwards the LSA to ...

Link-state routing protocol features 2.1.1  This page will explain how link-state protocols route data. Link-state routing protocols collect route information from all other routers in the network or within a defined area of the network. Once all of the information is collected, each router calculates the best paths to all destinations in the network. Since each router maintains its own view of the network, it is less likely to propagate incorrect information provided by any of its neighboring routers. The following are some link-state routing protocol functions: Respond quickly to network changes Send triggered updates only when a network change has occurred Send periodic updates known as link-state refreshes Use a hello mechanism to determine the reachability of neighbors  Each router multicasts hello packets to keep track of the state of the neighbor routers. Each router uses LSAs to keep track of all the routers in its area of the net...

Link-State Routing Protocol Overview of link-state routing 2.1.1 Link-state routing protocols perform differently than distance vector protocols. This page will explain the differences between distance vector and link-state protocols. This information is vital for network administrators. One essential difference is that distance vector protocols use a simpler method to exchange route information. Ooutlines the characteristics of both distance vector and link-state routing protocols. Link-state routing algorithms maintain a complex database of topology information. While the distance vector algorithm has nonspecific information about distant networks and no knowledge of distant routers, a link-state routing algorithm maintains full knowledge of distant routers and how they interconnect. The Interactive Media Activity will help students identify the different features of link-state and distance vector protocols. The next page will describe link-state routing protocols.

Overview The two main classes of IGPs are distance vector and link-state. Both types of routing protocols find routes through autonomous systems. Distance vector and link-state routing protocols use different methods to accomplish the same tasks. Link-state routing algorithms, also known as shortest path first (SPF) algorithms, maintain a complex database of topology information. A link-state routing algorithm maintains full knowledge of distant routers and how they interconnect. In contrast, distance vector algorithms provide nonspecific information about distant networks and no knowledge of distant routers. It is important to understand how link-state routing protocols operate in order to configure, verify, and troubleshoot them. This module explains how link-state routing protocols work, outlines their features, describes the algorithm they use, and points out the advantages and disadvantages of link-state routing. Early routing protocols such as RIP v1 were all distance...