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Activity 6.4.3: Troubleshooting a VLSM Addressing Design
Topology Diagram

Addressing Table Subnet HQ LAN1 HQ LAN2 Branch1 LAN1 Branch1 LAN2 Branch2 LAN1 Branch2 LAN2 Link from HQ to Branch1 Link from HQ to Branch2 Link from Branch1 to Branch2 Number of IP Addresses Needed 16,000 8,000 4,000 2,000 1,000 500 2 2 2 Network Address 172.16.128.0/19 172.16.192.0/18 172.16.224.0/20 172.16.240.0/21172.16.244.0/24 172.16.252.0/23 172.16.254.0/28 172.16.154.6/30 172.16.254.8/30

Learning Objectives:
• • • Discover errors in a VLSM design. Propose solutions for VLSM design errors. Document the corrected VLSM assignments.

All contents are Copyright © 1992–2007 Cisco Systems, Inc. All rights reserved. This document is Cisco Public Information.

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CCNA Exploration RoutingProtocols and Concepts: VLSM and CIDR

Activity 6.4.3: Troubleshooting VLSM Addressing Design

Scenario
In this activity, the network address 172.16.128.0/17 has been used to provide the IP addressing for the network shown in the Topology Diagram. VLSM has been used to subnet the address space incorrectly. You will need to troubleshoot the addressing that has been assigned for each subnet todetermine where errors are present and then determine the correct addressing assignments, where needed.

Task 1: Examine the Addressing for the HQ LANs.
Step 1: Examine the addressing assignment for the HQ LAN1 subnet and answer the questions below: 1. How many IP addresses are needed for the HQ LAN1 subnet? __________ 2. How many IP addresses are available in the currently assigned subnet?__________ 3. Will the currently assigned subnet fulfill the size requirement for the HQ LAN1 subnet? _______ 4. If the answer to the previous question is no, propose a new subnet mask that will allow for the correct number of IP addresses. ________________________________ 5. Does the subnet overlap with any of the other currently assigned networks? _______ 6. If the answer to the previous question isyes, propose a new subnet mask that will allow for the correct number of IP addresses without overlapping into any other subnets. ________________________________ Step 2: Examine the addressing assignment for the HQ LAN2 subnet and answer the questions below. 1. How many IP addresses are needed for the HQ LAN2 subnet? __________ 2. How many IP addresses are available in the currently assignedsubnet? __________ 3. Will the currently assigned subnet fulfill the size requirement for the HQ LAN2 subnet? _______ 4. If the answer to the previous question is no, propose a new subnet mask that will allow for the correct number of IP addresses. ________________________________ 5. Does the subnet overlap with any of the other currently assigned networks?_______ 6. If the answer to the previousquestion is yes, propose a new subnet mask that will allow for the correct number of IP addresses without overlapping into any other subnets. ________________________________

Task 2: Examine the Addressing for the Branch1 LANs.
Step 1: Examine the addressing assignment for the Branch1 LAN1 subnet and answer the questions below. 1. How many IP addresses are needed for the Branch1 LAN1 subnet?__________ 2. How many IP addresses are available in the currently assigned subnet? __________ 3. Will the currently assigned subnet fulfill the size requirement for the Branch1 LAN1 subnet? _______ 4. If the answer to the previous question is no, propose a new subnet mask that will allow for the correct number of IP addresses. ________________________________

All contents are Copyright © 1992–2007Cisco Systems, Inc. All rights reserved. This document is Cisco Public Information.

Page 2 of 5

CCNA Exploration Routing Protocols and Concepts: VLSM and CIDR

Activity 6.4.3: Troubleshooting VLSM Addressing Design

5. Does the subnet overlap with any of the other currently assigned networks? _______ 6. If the answer to the previous question is yes, propose a new subnet mask that will...