LAB 7 OSPF Open Shortest Path First A Routing Protocol Based on the Link State Algorithm OBJECTIVES The objective of this lab is to configure 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 Linkstate 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 neighbors 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 algorithm 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 sufficient 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 traffic 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 analyze 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 65 Network Simulation Experiments Manual 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 Configure the Network Initialize the network 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 66 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 finished 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 The PPP DS3 link has a data rate of 44 736 Mbps Configure the Link Costs We need to assign link costs to match the following figure 5 A 20 B 20 20 C 5 D 5 5 E F 10 5 G 10 10 H LAB 7 OSPF Open Shor test Path First Like many popular commercial routers OPNET router models support a parameter called a reference bandwidth to calculate the actual cost as follows Cost Reference bandwidth Link bandwidth 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 parameter used to configure 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 Configure Interface Metric Information 67 3 Assign 200000 to the Bandwidth Kbps field 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 field 5 Repeat for all links with a cost of 20 but assign 50000 to the Bandwidth Kbps field 6 Save your project Configure the Traffic Demands 1 Select both RouterA and RouterC by shift clicking on them a Select the Protocols menu IP Demands Create Traffic 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 traffic demand between RouterA and RouterC 2 Select both RouterB and RouterH by shift clicking on them a Select the Protocols menu IP Demands Create Traffic Demands Check the From RouterB radio button Change the color to red Click OK Click Create Network Simulation Experiments Manual Now you can see the lines representing the traffic demands as shown 3 To hide these lines Select the View menu Select Demand Objects Select Hide All Configure the Routing Protocol and Addresses 68 1 Select the Protocols menu IP Routing Configure Routing Protocols 2 Check the OSPF check box Uncheck the RIP check box Uncheck the Visualize Routing Domains check box as shown LAB 7 OSPF Open Shor test Path First 3 Click OK 4 Select RouterA and RouterB only Select the Protocols menu IP Routing Select Export Routing Table for Selected Routers Click OK on the Status Confirm dialog box 5 Select the Protocols menu IP Addressing Select Auto Assign IP Addresses 6 Save your project Configure the Simulation Here we need to configure some of the simulation parameters 1 Click on and the Configure Simulation window should appear 2 Set the duration to 10 0 minutes 3 Click OK and Save your project Auto Assign IP Addresses assigns a unique IP address to connected IP interfaces whose IP address is currently set to auto assigned It does not change the value of manually set IP addresses Duplicate the Scenario In the network we just created all routers belong to one