LAB3 Static Routing

7/31/2019 LAB3 Static Routing

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INTERNATIONAL UNIVERSITYSchool of Computer Science and Engineering

LAB 3: Static routing

Course: System and Network Administration Lecturer: Pham Van HauDate: Duration: 180 minutes

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IntroductionThere are two ways to route packets on a network. Either routes are written by the networkadministrator (static routing), or routes are defined dynamically thanks to useful routingprotocols (dynamic routing). This TP aims at giving you an overview of static routing. While staticrouting may be applied in small networks, this becomes impractical in larger ones. For theillustration purpose, we use the Linux machine as a router. In order to turn a Linux machine intoa router, two major things must be at least defined:

-its routing table

- its forwarding capacity from one interface to another. In Linux, this parameter can bechanged as follows:

o IP forwarding activated: $echo 1 > /proc/sys/net/ipv4/ip_forward (or the alias fw-

start)o IP forwarding deactivated: $echo 0 > /proc/sys/net/ipv4/ip_forward (or the alias fw-

stop)

Some useful commands you may need: route, netstat, traceroute, ifconfig, ping. Someexamples of the linux commands that you will use.

To view the routing table: netstat rn, or just route

Use route to modify the routing tableo To remove a route: route del -net 192.168.2.0 netmask 255.255.255.0 gw

192.168.2.1o To add a route: route add -net 192.168.2.0 netmask 255.255.255.0 gw

192.168.2.1

Configuration

The network architecture is given at the end of this document. In this lab, we use three

different Linux distribution :).

a) Nodes (web1, web2, web3): download dsl 4.4.10.isoWe use DSL (Damn Small Linux) www.damnsmalllinux.org/ distribution for thethree machines, called web1, web2, and web3. DSL is a light weight linuxdistribution. Steps to configure the machine.

Install hardware : while the machine is off, connect your ethernet card toVmnet 3.

start the machine

Open a terminal and become root: sudo su root
http://www.damnsmalllinux.org/http://www.damnsmalllinux.org/http://www.damnsmalllinux.org/http://www.damnsmalllinux.org/http://www.damnsmalllinux.org/


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Network configuration: Modify /etc/network/interface by adding the followinginformation at the end of the file.

iface eth0 inet staticaddress x.x.x.xnetmask x.x.x.xgateway x.x.x.x

Update configuration : Do ifup eth0 to update your network information.

b) Monitor (Ubuntu)We need a machine to monitor all the traffic. In order to do so, you need to installthe Wireshark program. Steps to configure the machine.

Connect your Ubuntu machine to the Internet and install wireshare: apt-getinstall ......wireshark.....

After installing wireshark, turn off the Ubuntu machine and add the two morenetwork interface cards to the machines and connect them to the network asdicpicted in Fig.1 (ask me if you don't know how to do it :) )

turn on the virtual machine.

Become root: sudo su root

Network configuration: modify file /etc/network/interfaces by adding thefollowing text at the end of the file.

######## Interface One ########auto eth0iface eth0 inet staticaddress X.X.X.Xnetmask 255.255.255.0broadcast X.X.X.255

network X.X.X.X######## Interface two ########auto eth1iface eth1 inet staticaddress X.X.X.Xnetmask 255.255.255.0broadcast X.X.X.255network X.X.X.X

######## Interface three ########auto eth2

iface eth2 inet staticaddress X.X.X.Xnetmask 255.255.255.0broadcast X.X.X.255network X.X.X.X

You need to turn on the three instances of wireshare to observe the traffic. Thatwill help you to answer the questions

c) RouterA, RouterB (Slitaz Linux) (download slizta-3.0.iso)


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Slitaz Linux (http://www.slitaz.org/en/) is another Linux distribution. We use it tomake router in this lab. Steps to configure the router.

Add one more network interface card and connect them as dicpicted in Fig.1

become root: Open a terminal and do su - (password is root)

Edit /etc/network.conf to configure the IP addressesYou will see in this file the configure information for the first interface. Thisinclude network interface, mode to obtain the IP address (dynamic/static),etc.You need to enter the similar items for your second network interface(eth1). For the both interfaces, you need to change all the default values toones described in your current document.

To update the IP address, type /etc/init.d/network.sh restart.

VerificationTest to ensure that

RouterA can ping machine web1, web2,

RouterB can ping web2 and web3.

Monitor can ping web1, web2, web3

TasksTask 1: From web1, ping web 2, is it working? Observe the packets exchanged on twointerfaces eth0 and eth1 of the monitor by using wireshark and explain what happen.

Task 2:Login to routerA. Think of the necessary conditions to make a Linux host act as a router (see

introduction). Are they satisfied? If necessary, modify the router configuration to satisfy these conditions and allowrouting of packets between web1 and web2. Describe and justify what you did. Observethe packets exchanged on two interfaces eth0 and eth1 of the monitor by usingwireshark and explain what happen.

Task 3: From web1, ping web3, is it working ? Observe the packets exchanged on threeinterfaces eth0, eth1, and eth2 of the monitor by using wireshark and explain whathappen.

Task 4:Login to routerA and routerB. As you did in question 2, perform all the necessary

modifications to allow routing of packets between web1 and web3. Describe and justifywhat you did.

Task 5: Ping again web3 from web1. Is it now working? If your answer is NO,reconsider what you did in question 4.

Task 6: Add the following host route in routerA routing table: IP 10.0.0.5 routed towardsinterface eth0. Now, ping this host from web1.

What is the path followed by the ICMP packet? Justify the routing mechanism.


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What kind of ICMP packets do you observe? Explain their meaning and try toexplain the reason for which they were generated.

Task 7: Ping web3 from web2, trace the path of the IMCP packet, explainTask 8: Do the following changes:On web3:

routing table: route add host 192.168.1.2 gw 192.168.3.50On your workstation:

fw-startDescribe the workstation routing table.Ping web3 from web1. Look at the Wireshark output and trace the path followed by theICMP packets.Justify the routing mechanism.

Fig.1

Web1:IP: 192.168.1.2

Web2:IP: 192.168.2.2

Web3:IP: 192.168.3.2

VMNet3

VMNet5

VMNet4

Eth0:192.168.1.1RouterA

Eth1: 192.168.2.1

Eth0:192.168.2.10RouterB

Eth1: 192.168.3.10

Eth0:192.168.1.50

Eth1:192.168.2.50

Eth2:192.168.3.50

Network 2:Network: 192.168.2.0/24Gateway: 192.168.2.1

Network1:Network: 192.168.1.0/24Gateway: 192.168.1.1

Network 3:Network: 192.168.2.0/24Gateway: 192.168.3.10

LAB3 Static Routing

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