65LAB OBJECTIVES The objective of this lab is to confi gure and analyze the performance of the Open Shortest Path First (OSPF) routing protocol. OVERVIEW In the RIP lab, we discussed a routing protocol that is the canonical example of a routing protocol built on the distance-vector algorithm. Each node constructs a vector containing the distances (costs) to all other nodes and distributes that vector to its immediate neighbors. Link-state routing is the second major class of intradomain routing protocol. The basic idea behind link-state protocols is very simple: Every node knows how to reach its directly connected neigh-bors, and if we make sure that the totality of this knowledge is disseminated to every node, then every node will have enough knowledge of the network to build a complete map of the network. Once a given node has a complete map for the topology of the network, it is able to decide the best route to each destination. Calculating those routes is based on a well-known algo-rithm from graph theory—Dijkstra’s shortest-path algorithm. OSPF introduces another layer of hierarchy into routing by allowing a domain to be partitioned into areas. This means that a router within a domain does not necessarily need to know how to reach every network within that domain; it may be suffi cient for it to know how to get to the right area. Thus, there is a reduction in the amount of information that must be transmitted to and stored in each node. In addition, OSPF allows multiple routes to the same destination to be assigned the same cost and causes traffi c to be distributed evenly over those routers. In this lab, you will set up a network that utilizes OSPF as its routing protocol. You will ana-lyze the routing tables generated in the routers and will observe how the resulting routes are affected by assigning areas and enabling load balancing. PRE-LAB ACTIVITIES & Read Section 3.3.3 from Computer Networks: A Systems Approach, 5th Edition . : Go to www.net-seal.net and play the following animation: ❍ Routing OSPF: Open Shortest Path First A Routing Protocol Based on the Link-State Algorithm 766 PROCEDURE Create a New Project 1. Start OPNET IT Guru Academic Edition · Choose New from the File menu. 2. Select Project and click OK · Name the project <your initials>_OSPF , and the scenario No_Areas · Click OK . 3. In the Startup Wizard: Initial Topology dialog box, make sure that Create Empty Scenario is selected · Click Next · Select Campus from the Network Scale list · Click Next three times · Click OK . Create and Confi gure the Network Initialize the network: 1. The Object Palette dialog box should now be on top of your project workspace. If it is not there, open it by clicking . Select the routers item from the pull-down menu on the top of the object palette. a. Add to the project workspace eight routers of type slip8_gtwy . To add an object from a palette, click its icon in the object palette · Move your mouse to the workspace, and click to place the object · Right-click when you are fi nished placing the last object. 2. Select the internet_toolbox item from the pull-down menu on the top of the object palette. Use the PPP_DS3 links to connect the routers. Rename the routers as shown · Close the Object Palette . ABCEGHD55551010 102020 205F Confi gure the Link Costs We need to assign link costs to match the following fi gure : The slip8_gtwy node model represents an IP-based gateway supporting up to eight serial line interfaces at a selectable data rate. The RIP or OSPF protocols may be used to automatically and dynamically create the gateway’s routing tables and select routes in an adaptive manner. The PPP_DS3 link has a data rate of 44.736 Mbps. Network Simulation Experiments Manual67 Like many popular commercial routers, OPNET router models support a parameter called a reference bandwidth to calculate the actual cost, as follows: C o s t = ( R e f e r e n c e b a n d w i d t h ) / ( L i n k b a n d w i d t h ) where the default value of the reference bandwidth is 1,000,000 Kbps. For example, to assign a cost of 5 to a link, assign a bandwidth of 200,000 Kbps to that link. This is not the actual bandwidth of the link in the sense of transmission speed, but merely a parame-ter used to confi gure link costs. To assign the costs to the links of our network, do the following: 1. Select all links in your network that correspond to the links with a cost of 5 in the preceding graph by shift-clicking on them. 2. Select the Protocols menu · IP · Routing · Confi gure Interface Metric Information . 3. Assign 200000 to the Bandwidth (Kbps) fi eld · Check the Interfaces across selected links radio button, as shown · Click OK . 4. Repeat for all links with a cost of 10 but assign 100000 to the Bandwidth (Kbps) fi eld. 5. Repeat for all links with a cost of 20 but assign 50000 to the Bandwidth (Kbps) fi eld. 6. Save your project. Confi gure the Traffi c Demands 1. Select both RouterA and RouterC by shift-clicking on them. a. Select the Protocols menu · IP · Demands · Create Traffi c Demands · Check the From RouterA radio button as shown · Keep the color as blue · Click Create . Now you should see a blue dotted line representing the traffi c demand between RouterA and RouterC . 2. Select both RouterB and RouterH by shift-clicking on them. a. Select the Protocols menu · IP · Demands · Create Traffi c Demands · Check the From RouterB radio button · Change the color to red · Click OK · Click Create . LAB 7 OSPF: Open Shortest Path First68 Now you can see the lines representing the traffi c demands as shown. 3. To hide these lines: Select the View menu · Select Demand Objects · Select Hide All . Confi gure the Routing Protocol and Addresses 1. Select the Protocols menu · IP · Routing · Confi gure Routing Protocols . 2. Check the OSPF check box · Uncheck the RIP check box · Uncheck the Visualize Routing Domains check box, as shown: Network Simulation Experiments Manual69 3. Click OK . 4. Select RouterA and