Transcript
Packet Tracer 3 Lab – VLSM 2 – Solution
Objective • • • •
Create a simulated network topology using Packet Tracer Design an IP addressing scheme using a Class B subnetwork address and VLSM Apply IP addresses to the routers and workstations in the simulation Test the simulated topology to verify IP connectivity
Background / Preparation You are responsible for designing a network that connects 3 geographically separated sites, each with its own LAN, to the corporate headquarters for access to the Web Server. The connection will be made through a Cloud representing an ISP / Internet network connection at each site. You will configure IP addresses to the border routers represented by the cloud. The service provider has assigned a portion of a class B network address (1,024 addresses) to work with and must make the best use of the address space while minimizing wasted addresses. To accomplish this you will develop an IP addressing scheme using Variable Length Subnet Masks (VLSM) to allocate IP addresses to the LANs and WAN links in the network. You will apply the addresses to the routers and workstations in the simulated network and then test to ensure that it works. Routers simulated with Packet Tracer use RIP version 2 to find routes to remote networks automatically. A router advertises all networks that its ports belong to, which is specified by the IP address and subnet mask. RIP version 2 supports VLSM. RIP keeps a routing table of remote networks. The routing table associates a network (network ID and subnet mask or network bits) to the port that is closest to the network. A router can have one default port. A Cloud simulated with Packet Tracer has multiple borders. Each border is a WAN port that has an IP address. The cloud provides the DCE clocking for each of its border interfaces by default. A cloud does not have a default port. All other cloud functions are identical to router functions. It is recommended that you become familiar with the basic features of Packet Tracer prior to starting this lab by running the tutorials found under the Help menu option in Packet Tracer. 1-6
Packet Tracer 3 Lab – VLSM 2 Solution
Copyright 2004, Cisco Systems, Inc.
Step 1. Design an IP Addressing Scheme Using VLSM Starting with the Class B subnetwork address of 172.16.8.0/22, create subnets to allocate IP addresses to the Ethernet LANs and WAN links in the network topology shown above. The requirements for the number of addresses are listed in the table below. Use VLSM to minimize wasted IP addresses. Assume ip subnet-zero is enabled and that the first subnet (all zeros) and last subnet (all ones) can be used. As a general rule it is best to first allocate subnets to the networks with the largest number of required addresses starting from the lowest subnet number and working up. Ethernet networks will require more IP addresses than WAN links. Be sure to minimize the number of addresses used on the WAN links and allocate WAN subnets starting at the highest subnet. Document your VLSM subnet design using the table below. You will use these subnet address ranges to assign interface addresses to the routers and workstations in the scenario.
Address Area
Number of IP Addresses
32 Bit Address Prefix and Slash (/) Bit Mask
32 Bit Dotted Decimal Subnet Mask
Class B Subnetwork Assigned
1,024 total (1,022 useable)
172.16.8.0 / 22
255.255.252.0
210 hosts
172.16.8.0 / 24
255.255.255.0
195 hosts
172.16.9.0 / 24
255.255.255.0
95 hosts
172.16.10.0 / 25
255.255.255.128
52 hosts
172.16.10.128 / 26
255.255.255.192
2 hosts
172.16.11.240 / 30
255.255.255.252
2 hosts
172.16.11.244 / 30
255.255.255.252
2 hosts
172.16.11.248 / 30
255.255.255.252
2 hosts
172.16.11.252 / 30
255.255.255.252
Router 0 LAN Router 1 LAN Router 2 LAN Router Corp LAN Router 0- Cloud WAN Router 1- Cloud WAN Router 2- Cloud WAN Router Corp – Cloud WAN
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Packet Tracer 3 Lab – VLSM 2 Solution
Copyright 2004, Cisco Systems, Inc.
Step 2. Create the Basic Topology a. Open the Packet Tracer application to begin creating the simulated topology. The topology consists of 4 routers interconnected through the cloud by WAN serial links. A single workstation on each LAN represents the group of IP addresses required as indicated in the table in step 1. The connection between the workstations and routers is assumed to be a switch or hub. b. Verify Simple Mode. Click on the Options menu and verify that Simple Mode is selected. The figure below shows the networking device icons available to create topologies. The Connect lightning bolt icon is used to link the devices. The Remove pencil eraser icon can be used to delete any device or link.
c.
Place the routers in the topology and rename a router From the Topology Tab, click and drag a Router icon to the workspace and click again to paste it in position. Repeat this until the four routers shown in the diagram are present. You may also double click the router icon and then click 4 times to paste multiple icons in the workspace. Click the Cancel icon in the lower right corner when finished or to abort an operation. The four routers are initially named Router 0, Router 1, Router 2 and Router 3. Click on Router 3 and Change the name to Corp.
d. Place the workstations in the topology and rename a PC From the Topology Tab, click and drag a PC icon to the workspace and click to paste it in position. Repeat this until the four PCs shown in the diagram are present. You may also double click the PC icon and then click 4 times to paste multiple icons in the workspace. Click the Cancel icon in the lower right corner when finished. The four PCs are initially named PC 0, PC 1, PC 2 and PC 3. Change the name of PC 3 to Web Server. When a PC is directly connected to a router in Packet Tracer, as shown in the diagram, the existence of a hub or switch is assumed.
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Packet Tracer 3 Lab – VLSM 2 Solution
Copyright 2004, Cisco Systems, Inc.
Step 3. Connect the Networking Devices Note: By default, each Packet Tracer router has 4 Ethernet and 2 Serial ports numbered as shown in the figure below. Ports 0 and 1 are RJ-45 Fast Ethernet, ports 2 and 3 are D-Connector type Serial and ports 4 and 5 are Fiber Fast Ethernet. In the figure below Serial Port 2 is selected with the Port Config options displayed. This port is enabled (status=on or not shut down), bandwidth is 1.544 Mbps and DCE clocking is disabled. In the example below, an IP address and subnet mask have been entered. Ports can be added or removed as desired.
a. Create the WAN Links
Click on the Connect lightning bolt icon to create the WAN Link between router 0 and the Cloud. When the Connect icon is selected in Simple Mode it does not prompt for the connection type and it is not necessary to select the port to use. For router-to-router connections, the next available Ethernet port is used by default. For router-to-cloud connections the default is the next available Serial port. Repeat this process for the WAN connection to the Cloud for Routers 1, 2 and Corp. It is not necessary to set the clock for any of the routers since the cloud interfaces already default to DCE.
b. Create the LAN Links
While in Simple Mode, click on the Connect lightning bolt icon. Select first Router 0 and then PC 0 to create the LAN Link between them. Repeat this process for the other routers and PCs. The Interface status indicator dots between routers and PCs should all be green. The existence of a hub or switch between a router and PC is assumed.
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Packet Tracer 3 Lab – VLSM 2 Solution
Copyright 2004, Cisco Systems, Inc.
Step 4. Configure IP Addresses on the Routers and Workstations
a. Assign Router and Cloud IP Addresses
Select Router 0 and click on Ethernet Port 0. Enter an IP Address and subnet mask for the LAN interface from the VLSM subnet scheme developed in step 1. Next select Serial Interface 2 and enter an IP Address and subnet mask for the WAN interface. Repeat this process to assign IP addresses and subnet masks as appropriate for the LAN and WAN interfaces of the other three routers. Assign IP addresses and subnet masks to the four cloud ports. Use the table below to record your IP addresses for the router and cloud interfaces.
Device Router 0
Interface Ethernet port 0 Serial port 2
IP Address 172.16.8.1 172.16.11.241
Subnet mask 255.255.255.0 255.255.255.252
Router 1
Ethernet port 0 Serial port 2
172.16.9.1 172.16.11.245
255.255.255.0 255.255.255.252
Router 2
Ethernet port 0 Serial port 2
172.16.10.1 172.16.11.249
255.255.255.128 255.255.255.252
Corp
Ethernet port 0 Serial port 2
172.16.10.129 172.16.11.253
255.255.255.192 255.255.255.252
Cloud
Serial port 0 Serial port 1 Serial port 2 Serial port 3
172.16.11.242 172.16.11.246 172.16.11.250 172.16.11.254
255.255.255.252 255.255.255.252 255.255.255.252 255.255.255.252
b. Assign Workstation IP Addresses
Select PC 0. Ethernet Port 0 should be the only port available. Enter an IP Address and subnet mask for the PC from the VLSM subnet scheme developed in step 1. Next enter the IP address of the Gateway. This is the IP address of the Router 0 Ethernet LAN interface. Repeat this process to assign IP addresses, subnet masks and gateways as appropriate for the other PCs.
Device PC 0 PC 1 PC 2 Web Server
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Interface Ethernet port 0 Ethernet port 0 Ethernet port 0 Ethernet port 0
IP Address 172.16.8.2 172.16.9.2 172.16.10.2 172.16.10.130
Packet Tracer 3 Lab – VLSM 2 Solution
Subnet mask 255.255.255.0 255.255.255.0 255.255.255.128 255.255.255.192
Gateway IP Address 172.16.8.1 172.16.9.1 172.16.10.1 172.16.10.129
Copyright 2004, Cisco Systems, Inc.
Step 5. Test the IP Addressing VLSM Scheme
a. Click on the Simulation Tab and click on the Add Packet button, which has a Plus (+) sign and a small envelope next to it. A packet will display on the timeline that says “defining” next to it.
b. Click on source PC 0 and then click on the destination Web Server. The timeline window should show a colored packet with “PC 0 >> Web Server” next to it.
c. Click on the blue right arrow button in the white square of the player controls, shown in the figure
above, to simulate a ping. This will send the packet from PC 0 to the Web Server and test IP connectivity. The packet should pass through all devices in the path and reach the Web Server. A green check mark will display on the Web Server if the ping is successful.
d. To complete the testing, click on the Add Packet icon again and test connectivity from PC 1 to the
Web Server. Add a third packet and test from PC 2 to the Web Server. Each new packet will be assigned a different color. Also send packets from PC 0 to PC 1 and PC 2. Click on the New button if you wish to start a new series of packets.
e. If the pings are not successful, troubleshoot the IP addressing scheme and addresses/subnet masks assigned to ensure that they are compatible.
Step 6. Save the Topology
a. Click on the File Menu and click Save. Save the topology under the Name of VLSM2-XXX where XXX is your initials.
Step 7. Reflection a. What would have happened in the simulation if IGRP was used as the routing protocol? IGRP does not pass subnet information in its updates. It would not have been possible to ping from PC 0 to the Web Server due to multiple subnet masks (VLSM). b. Could the network have been subnetted and still provide an adequate number of IP addresses for each network without using VLSM? Yes. 8 networks were required (4 LANs and 4 WANs). If the minimum number of 3 bits were borrowed, the number of possible subnets would be 8 (using subnet zero and the all-ones subnet). This results in 8 subnets with 254 usable host IPs each. The maximum number of hosts required was 210 on the LAN on Router 0. There would be no additional subnets for future growth and a large number of IP addresses would have been wasted. c.
How many addresses would have been wasted if the network 172.16.8.0/24 was used for the WAN link between Router 0 and Router 1? This would allocate 254 IP addresses to the WAN link which requires only 2 thus wasting 252 IP addresses on the link.
d. Can you think of other ways to use Packet Tracer to test scenarios? Packet Tracer can be used to test many varied Ethernet, Serial and Wireless scenarios at the MAC (data link) and IP (network) layers. 6-6
Packet Tracer 3 Lab – VLSM 2 Solution
Copyright 2004, Cisco Systems, Inc.
