CISCO packet tracer is a self-paced, visual, interactive teaching and learning tool and a network simulation software. In the simulation and visualization mode we can see and control time intervals, transfer of data inside and also across the network. The real time mode is the one in which the equipment can be configured before working.
Static Routing Protocol, RIP, and OSPF:-
Static routing protocol is used to configure routers in the computer networks. It is characterized by the absence of communication between routers. Dynamic is opposite to that of static routing.
RIP is a dynamic routing protocol used in LAN and WAN. It is classified under interior gateway protocol. It uses distance vector routing algorithm. It has three versions RIPv1, RIPv2 and RIPng. Version1 does not carry subnet information, hence support class full addressing. Version2 carry subnet information hence support class less addressing.
OSPF is also a dynamic routing protocol used in IP network. It is based on the link state shortest path first algorithm. It is used in global internetworks.
To study the basic concepts of network routing and to configure both static and protocol controlled routing using RIP and OSPF
First we need to open the windows operating system and then copy the file “CE784 routing.pkt” into the folder and make 3 copies for 3 lab sessions.
Using CISCO packet tracer software open the session one by one. Once we open the file using the software, we see a network connecting routers and PC's as shown below. The routers can be configured using command line interface (CLI). In order to enable the router just type “enable” command in CLI prompt. Without enabling the router, the CISCO router does not allow any other commands to work. In order to configure particular router just type “conf tab term” command a list of configure command displayed on the screen. The characteristics of protocols such as static routing protocol, router information protocol (RIP), and open shortest path first (OSPF) protocol are explained using tasks and tests.
TASK1:- Test Connectivity
Ping command in CLI is used to test the network connectivity. But connection can be both successful and unsuccessful. The figure below shows the “ping” command being successful and unsuccessful.
Ping is successful when it sends 5 ICMP packets which are denoted by “!”. This is done by the help of routers and dots. Ping is unsuccessful when it does not send any ICMP packets which are denoted by “.”
Reason behind successful ping is that the IP address is directly connected to the routers. Whereas in unsuccessful ping the IP address is not directly connected to the routers.
TASK2:- Configuring a basic static route
Using the command “show ip route” we can display the routing table of a router which shows the list of various codes. The below figure shows the all the members in the routing table and shows the connection of router1 to all other networks. Configuring a basic static route uses two modes privilege mode and global configuration mode. Privilege mode has various show commands and testing commands. The global configuration mode is used to make changes in the router. “The general syntax for the static root is IP route destination net ID subnet mask gateway address”. To define a static route to a particular router type the IP address followed by subnet mask and gateway address of that router. The figure below shows that the connection has established. In the figure the ‘c' indicates it is a direct connection to the network and‘s' indicates that the network 22, 44, 24, 33, 34 are connected to network 12 through the gateway 12 network.
The static route is configured in router4. It is done by writing route4 address followed by subnet mask and then gateway address as
192.168.24.0 255.255.255.0 192.168.12.2
Simulation mode is used to study the movement of packets between the routers. The figure above shows the packet movement. The packets are lost without reaching the router4 because static route is not configured in router4, but was configured only in router1.
TASK3:-Configure static route
In this task we need to configure all the static routes by using commands in CLI mode. Using a separate command the routers which are not connected directly are connected. In the figure shown in task1, the router1 is directly connected by the networks 192.168.11.0 and 192.168.12.0.the remaining networks has to be configured manually. Consider router3 which is connected directly by the networks 192.168.23.0, 192.168.33.0, and 192.168.34.0 and the networks remaining 192.168.11.0, 192.168.12.0, 192.168.22.0, 192.168.24.0, and 192.168.44.0 are configured manually. When all the networks are connected the connection can be tested using ping between routers and hosts.
The routing table of router2 is shown below after static route configure and check the connections by using ping.
TASK4:- Opening Interface of a Link
In the figure shown in task1, there is a direct link between router2 and router3 whose interface was shutdown. In order to open that interface we need to type interface type interface _number. 1st we need to enable the link in router2, for that we need to enable the router2 and then enter the command “interface serial 0/1/0” in the CLI and then type the command “no shutdown” link is ready from router2. Same procedure is to be repeated at router3. The command shutdown is used to link two routers. The link between router2 and router3 can be verified by pinging. The figure shows how the link is enabled between roter2 and router3.
Enter configuration commands, one per line. End with CNTL/Z.
Router2 (config)#interface serial0/1/0
Router2 (config-if)#no shutdown
Enter configuration commands, one per line. End with CNTL/Z.
Router3 (config) #interface serial0/0/1
Router3 (config-if) #no shutdown
TASK5:- Effective Routing and Intelligent Path Selection
This task is all about path selection in the network given. Consider the path between router1 and router4 there are 2 different paths. The 1st path is from router1 to router2 and then from router2 to router4. The 2nd path is from router1 to router2 and then from router2 to router3 and finally from router3 to router4, which seems to be very long because of more no of hops. But link between the router2 and router3 has 1Mbps bandwidth and also the link between router3 and router4 is also 1Mbps bandwidth. Therefore select the 2nd path for the packets to travel in both the direction. Hence router 2 and router4 should be configured again with the gateway that allows the packets through router3. The link between router2 and router3 is established.
Since, we need to configure manually every router it is complex process and also time consuming. It is a undeveloped form of routing like each router is manually configure, which is time consuming and guaranteed error formation. Hence static routing cannot be used for practical working.
TASK6:-Dynamic Routing With RIP
Start this task with new session i.e.; make a new copy of the original copy. Then go to simulation mode and for router1 turn on the RIP protocol using the commands below.
Enter configuration commands, one per line. End with CNTL/Z.
Router1 (config) #router rip
Router1 (config-if) #network 192.168.11.0
Router1 (config-if) #network 192.168.12.0
Router1 (config-if) #
RIP can be configured very easily, by looking at the networks that are directly connected to the router. It is configured in this interface, where the router creates a router table and gets the RIP updates from the routers next to it. The command “debug ip rip” is used to check all the updates. Once router1 is configured we can verify that RIP is configured. It can be checked by using the command show ip route. Packets being broadcasted from router1 is shown in the figure below.
TASK7:-RIP For All the Routers
In this task we need to configure RIP for all the routers as we did in task 6 for router1.the figure shows the routing table for router4. Once all the routers have been configured check for connectivity using ping command. Router4 is configured with RIP as shown below and RIP database of router4 is also shown below.
TASK8:-Packets Used in RIP
TASK9:-Sensible Route Selection by RIP
In this task we discuss whether the RIP chooses a sensible route or not. The command “trace route” is used to derive the routes between all the pairs of routers. Flow of packets is studied using simulation mode. Ping command can be used to see the packets and their flow path. The route used in network topology from router1 to router4 is router1 to router2 via network gateway 192.168.12.0 and then connected to router3 through the gateway 192.168.23.0 and then reaches the router4. But RIP uses the sensible path from router1 to router4 that is, from router1 to router2 and then to router4 via gateway 192.168.24.0 which is less sensible due to line bandwidth. Because it only calculates the number of hops counts in the routes which suppose to be only 2 hop counts present in it, but which is a very slow connection of 64Kbps speed and which is of very high cost. Even if the path router1-router2-router3-router4 is of very high connection with the bandwidth of 1Mbps and which has very low cost. This is the biggest disadvantage in the RIP choosing the sensible route.
TASK10:-RIP and Recovery Failure
Simulation is turned on. Then we need to disable the link between router2 and router3 by “shutdown” command in CLI. Then connect the link using “no shutdown” command and once packets are exchanged and captured. The recovery time is noted down. The above figure shows that the network 192.168.23.0 is the link between the roter2 and router3 is removed and recovery time is about 6 seconds. And when the network 192.168.23.0 link between router2 and router3 is opened the recovery time is 30 seconds as shown above.
TASK11:- Introducing Erroneous Address
in this task we need to change the ip address of the router to a new address which is 172.16.1.1 with the subnet mask of 255.255.255.0. Then we need to check whether the network as accepted the new address by pinging. Then router4 is is also given a new ip address as 172.16.2.2 with the subnet mask 255.255.255.0. Ping both the IP addresses and these two routers are configured with RIP using new IP address. Then ping 126.96.36.199 from router3. The updates are received from both the router 1and 4 when the debug command is on in router2. Two routers send updates about the network 172.16.0.0. RIP protocol does not know about the two networks 172.16.1.0 and 172.16.2.0 with the same subnet mask. When IP address are pinged alternatively some packets return and some fail. The figure below shows ping operation.
Ping being unsuccessful and unable to connect to networks is that it is working in version1. RIP version1 is a class full protocol which can detect the classes automatically. If address is in class A, then 1st octet is netid and next 3 octets are hostid. If the address is class B, then 1st two octets are netid and next 2 octets are hostid. Due to subnet mask address the class B address is taken as 172.16.0.0 and this is the reason why the router2 is receiving the updates from 2 routers in different direction.
TASK12:- RIP Version 2
In this task we need to open a new copy of the original file for new session. RIP is configured in all the routers, but it is version 2. Then all the networks are added in CLI, and then command version 2 is added in the next line and there is necessary 3rd command. In RIP it automatically assumes the class of the given IP address and hence it is turned off. The router2 and router3 link is opened. Errors are introduced same as in the previous task and check connectivity in routers. At router2 packets are analyzed and IP address 172.16.1.0 and 172.16.2.0 are pinged. Both the address are received from different routers separately. The figure below gives the routing update received by router2 and ping being successful for new IP address.
Hence RIP is a distance vector protocol which calculates the hop counts to choose the path. Configuring the router using RIP is easier than configuring using static routing protocol. The disadvantage of RIPv1 is classless addressing which can be overcome by RIPv2.
TASK13:- OSPF Configuration
In this task the network router which is not configured by any protocol is taken. The router1 is configured with OSPF. It is same as RIP configuration. This command “router ospf 1” changes from global configuration mode to OSPF mode. Configuration can be verified using the routing table. The number “1” indicates the protocol running in that router and for different routers the number can be same or different. If it has same number then it is in the same AS. The command “network 192.168.0.0 0.0.255.255 area 0.0.0.0” is entered next. The 1st address is the netid and its not a whole address and the next address is the wild card mask. In this, it is wild card mask when bit is 0 and it cannot be altered. If all the bits are 255 then the bits can be altered.
TASK14:- To Turn on OSPF in the Routers
Same command is used as used above that is “router ospf 1” to turn on the router1 and also to turn on all the routers. The link between the router2 and router3 is opened and router has the information of the link in link database. To test the connectivity of router many tests are taken such as conformance test, route convergence test, and equal cost path verification test, etc. routing table tells that all the networks are included.
TASK15:- Test Connectivity
In this task we find other method to test the connectivity using ping and trace route. To test connectivity for routers and hosts, the ping was done from host to host. This is similar to that of static routing protocol and the difference is the command prompt and the ping sends only 4 packets instead of 5 packets. The figure below displays the result.
Trace route is also used to study about the path taken by the routers. It is used to test connectivity and troubleshooting.
TASK16:- OSPF Path Selection
In this task the OSPF chooses its sensible path same as the RIP did. Try to see whether the OSPF choose the sensible path between the router, we use the trace route command in CLI of router4. The most sensible path from router1 to router4 is router1-router2-router3-router4 which is of high bandwidth 1Mbps and less cost. The OSPF choose this path which is more sensible. It is followed by all the routers. The figure below shows the trace route from router1 to router4. OSPF is more primitive protocol like RIP and hence it is used practically.
TASK17:- OSPF Recovery from Failure
In this task we need to 1st shutdown the link between the router2 and router3 using the “shutdown” command and then changes are present which can be studied using the simulation mode. When the link was broken the network becomes whole. The routing updates are sent telling that the link was broken and it is using the alternate path. It is done immediately by sending the updates to all the routers. Once the link was opened the result was shown in the figure below.
Like RIP the OSPF does not exchange the routing table frequently but advertises the changes in the network. This is the response given by the OSPF when there is network change. OSPF uses alternate path when there is change in the network. OSPF is the best protocol amongst the three protocols and used in large networks.
1. The routing protocol laboratory sheet provided in the lab.
2. The routing in the internet, Christian Huitema , second edition.