CS312 LAB 3 - CONFIGURING A ROUTER

Transcription

1 CS312 LAB 3 - CONFIGURING A ROUTER Be sure to leave the lab connected in the same way that you found it. If you change the configuration of the network, it may be difficult for the next person to complete the lab. After completing this lab, you should be able to: 1. Understand the capabilities of a router 2. Set up and configure a router 3. Be able to set TCP/IP parameters on a Linux system or PC Background Information In this lab you are going to do the setup and configuration of three routers and the establishment of IP addresses for the Linux workstations in the lab. Design: In this lab, you are going to connect three networks together via a backbone that connects three routers. There are four Linux machines. Using the hubs available, connect PC1 and PC2 into one hub, PC3 into a second hub and PC4 into a third. Be sure to use hubs, not switches! You will define new network numbers for the three segments using the class A private network numbers defined in RFC We will subnet the network using a mask of Use the range of class A private subnetworks: to Randomly choose 4 of these network numbers to use. There are three routers in the lab. One network is to be to be connected to each router. A fourth network will connect the routers(using a hub) and thus will have no other hosts on it (hence you need four networks). EXERCISE1: Network diagram 1. Draw a diagram of how you intend to interconnect the machines 2. For each network, list the network address, set of machines and router interfaces : Network Network Addreess Machines/ Router interfaces in network N /24 PC1, PC2, R1(FastEthernet0/1) N2..

2 EXERCISE2: PC IP Address Selection 1. Identifying the network addresses of each of the machines. PC IP Address chosen PC1 PC2 PC3 PC4 2. Identify which ports you will be using on the routers and the IP addresses of those ports. Router port/interface Network associated IP Address chosen R1 FastEthernet0/0 R1 FastEthernet0/1 R2 FastEthernet0/0 R2 FastEthernet0/1 R3 FastEthernet0/0 R3 FastEthernet0/1 R4 FastEthernet0/0 R4 FastEthernet0/1 Update your drawing to incude ip addresses of all PCS and router interfaces. ***************************************************************** Be very careful to follow the directions in this writeup. Do not change any of the passwords for any of the devices! For all of the machines, MAKE NOTE OF THE CURRENT SETTINGS SO THAT AT THE END OF THE LAB YOU CAN RECONFIGURE THE MACHINES TO THEIR ORIGINAL VALUES! ***************************************************************** EXERCISE3: Manual Wiring according to diagram Physically hook up your network according to the diagram that you have drawn. EXERCISE4: Configure PCs Assign PC ip addresses Assign proper IP addresses you chose to all PCS. On the Linux boxes: You can log into any of the Linux boxes as netlab (password netlab). Do not change the password!

3 Use su to become root. su - (Remember the -) To configure the network interfaces for the Linux workstations, the following must be done. 1. Identify the name of the network interfaces. There may multiple interfaces and they are known by different names on different systems. To find the network interfaces available you can use the command: netstat -ain (Look at the man pages for netstat to determine what the options do) One interface that is listed will be lo, which is the virtual interface for what is called local loopback (a way for a machine to treat itself as one of the machines on the net just like any other) and should have an address of Any others should be names of physical network interfaces and should show an ethernet address. Set up the interfaces by using the /sbin/ip addr add <address/mask> dev <int> Set default routes In addition, we need to set the default route for each Linux box so that it knows what address to send packets that are destined for other networks. Since each box is attached to only one router, we can simply set a default route in the Linux box to send messages to the router address that is on its network. To do this, you use the route command (do a man route to see details). The command is used as: ip route add default via <router_address> If we have a network of , and the router that is attached to that network has the address , then we use the command : ip route add default via ip route add /16 via To delete a route that has been set up, use ip route del <route> <router_address> ip route del /16 via dev eth3

4 ip route del default via You can also use ip route show to display the current routing table. To delete a route that has been set up, use ip route del default gw <router_address> List the default gateway ip chosen for each PC PC Default Gateway IP PC1 PC2 PC3 PC4 EXERCISE5: Configure Routers CISCO IOS basics: The command line interface of IOS has a rich syntax. There are hundreds of configuration commands and some commands have numerous options. The command line interface runs in different modes and each command requires a certain mode. Each command mode has a different prompt and you can tell which mode you are in by looking at the prompt. Typing a question mark at any prompt will give you a list of available commands for that mode. If a command requires parameters, you can get an idea of the parameters required b typing the command followed by a question mark. Note: When making selection within the router configuration application, you can abbreviate entries as long a they are not ambiguous (e.g. "int" for "interface") Physically connect the serial cable (blue flat cable) from the serial port on the back of a Linux box (use PC1) to the router jack labeled console on Router1. This is a communications link that allows you to configure the router. On the Linux box, open up a terminal emulator program by typing minicom on the command line. This should open a connection to the router and you should see a prompt of Router1> This is in the user EXEC mode. To see the commands that are possible in this mode, enter a question mark: Router1>? To view and change system parameters, you need to enter the Privileged EXEC mode. To do this, type the word enable and then the password to the enable mode: netlab

5 Router1> enable Password: netlab Router1# Notice that the prompt has changed indicating that you are in the Privileged EXEC mode. As before, you can enter a question mark to see what commands are available. To modify system wide configuration parameters, you need to enter the global configuration mode. This mode is entered by typing Router1# configure terminal Router1(config)# The routers we are configuring have two ports or interfaces. Note the names of the two ports on the back of the router. To make changes to a network interface, enter the configuration mode by using the keyword interface along with the name of the interface you want to configure. Router1(config)# interface FastEthernet0/0 Router1(config-if)# To return from the interface configuration to the global configuration or from the global configuration to the Privileged EXEC mode, use the exit command. Router1(config-if)# exit Router1(config)# exit Router1# Each time you enter exit, it will take you one more step up the hierarchy. To directly return to the Privileged EXEC mode from any configuration mode, type end Router1(config-if)# end Router1# To return from the Privileged EXEC mode to the user EXEC mode, type the command disable Router1#disable

6 Router1> To terminate the console session from the user EXEC mode, type logout. Router1> logout Router1 con0 is now available Press Return to get started Alternatively, you can type logout or exit from the Privileged EXEC mode. Configuring an Interface 1.To assign address to interface/port FastEthernet0/0 of Router1: Router1> enable Password: netlab Router1# configure terminal Router1(config)# no ip routing Router1(config)# ip routing Router1(config)# interface FastEthernet0/0 Router1(config-if)# ip address Router1(config-if)# no shutdown Router1(config-if)# end The no ip routing disables IP forwarding and resets the contents of the routing table. The ip routing command enables ip forwarding on the router. The end command enables the interface. The command shutdown would disable an interface. When you have finished, use the commands to verify ip addresses are setup and interface is up: Router1# show interfaces Router1# show running-config 2. Do same for FastEthernet0/1 port of Router 1 to assign the ip address you selected in Exercise2 for it. Repeat steps 1,2 for Router2 and Router3 to assign ip addresses you chose in Exercise2 for each port: i.e Do the same with Router2 and Router3 (you need to Physically connect the serial cable (blue flat cable) from the serial port on the back of PC1 to the router jack labeled console on Router2 (or Router3))

7 According to your diagram, you should now configure all the appropriate interfaces of the three routers. Be sure that you match the network numbers and masks correctly on each of the interfaces according to what networks they are connected to according to your diagram. In your report, include the output from these commands (for Router3) along with a brief explanation of what it means. EXERCISE6: Test Connectivity From PC1, ping PC2, and both IP addresses of the router that is connected to the same network as PC1. Do the same thing from PC3. Finally, from Router1, try to ping each of the 4 devices along with both IP addresses of Router2. In your report, Include the result of your pings along with a brief explanation. You should also indicate which devices you can successfully reach and if this matches your expectations. EXERCISE7: Creating routing Tables Even though we have enabled ip routing on the routers, we have not created any routing tables! We will add static routes to begin. The following commands can be used: From the Privileged EXEC mode show ip route Displays the contents of the routing table clear ip route * deletes all routing table entries show ip cache shows the contents of the ip cache From the global configuration mode: ip route-cache Enables route caching. By default, route caching is enabled on a router no ip route-cache disables route caching ip route destination mask gw_address adds a static routing table entry to destination with netmask mask. Gw_address is the address of the next-hop router ip route destination mask iface adds a static routing table entry to destination with netmask mask. Here the next-hop information is the name of a network interface(e.g. FastEthernet0/0) no ip route destination mask gw_address no ip route destination mask iface deletes the route table entry with destination, mask, and next hop

8 Add static routing entries to routing table For each router now we need to add static routing entries to reach networks that it is not directly connected. E.g. Router1 need to add two static entries, one to reach network2(with PC3), and the other to reach network3(with PC4). E.g. add static route from Router1 to Network PC FE0/0-Router1-FE0/ FE0/0-Router2-FE0/ PC2 Router1(config)#ip route Note that Router1 is directly connected to Network2. So, a static entry in routing table of Router1 for Network2 is not needed! Add default route to routing table: Router1(config)# ip route This sets a default route so that any address that does not match one of the other entries will automatically be routed to Remove static route from routing table: Router1(config)# no ip route This removes this route from the table Display contents of routing table: show ip route Add the routing entries to each of the routers so that all the networks are reachable. In your report, copy output you got for following commands in Router1 with a brief explanation: show ip route show ip cache Network1 Network2 Network3

9 EXERCISE8: Test Connectivity At this point, all boxes should be able to communicate with each other. Send a ping command from PC1 to all the other interfaces (3 other linux boxes and 6 ports on the routers). If not all of the addresses are reachable, you will need to troubleshoot the network and try to determine where the problem is. When you have successfully debugged the network, repeat the ping from PC1 to the 3 other linux boxes and the four ports and save the output. Include it in your report with a brief explanation. In your report, copy output you got for ping from PC1 to other 3 PCS along with an explanation: EXERCISE9: Looking at forwarded packets Now move PC4 from its network to the network that connects the two routers. Note that its IP address must be changed to match the network that it will now be on. Start wireshark on PC4. Send a ping from PC3 to PC1. Look at the packets from the ping on wireshark. Carefully look at the MAC address and the IP address of the ping and the response. Check to see what the MAC addresses of PC1, PC3 and the two routers are. Attach your wireshark results to your report along with an explanation of what you have found. In your report, give a brief overview of what you have covered and learned. Include the appropriate output along with explanations for each portion of the lab. Be sure to have both an introduction and a conclusion to your report. Be sure to disconnect all wires and remove all files that you created. Finally, reset the tables for the routers and reboot the machines so the lab will be ready for the next group. Submitting Lab Report Submit only one lab report per group. The name of the report should be Lab3_Report_first_last.pdf where first and last represent the name of one member (selected at random) of the group(e.g. Lab2_Report_John_Doe.pdf). The list of names and s of the group members should be included in the first page of the report. To submit, copy the file to /usr/people/handin/cs312 folder by the due date listed in the class website.