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© 2008 Cisco Systems, Inc. All rights reserved.Cisco ConfidentialPresentation_ID 1 Chapter 9: Subnetting IP Networks Introduction to Networking 9.0.

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Presentation on theme: "© 2008 Cisco Systems, Inc. All rights reserved.Cisco ConfidentialPresentation_ID 1 Chapter 9: Subnetting IP Networks Introduction to Networking 9.0."— Presentation transcript:

1 © 2008 Cisco Systems, Inc. All rights reserved.Cisco ConfidentialPresentation_ID 1 Chapter 9: Subnetting IP Networks Introduction to Networking 9.0

2 Presentation_ID 2 © 2008 Cisco Systems, Inc. All rights reserved.Cisco Confidential Chapter 9 9.1 Subnetting an IPv4 Network 9.2 Addressing Schemes 9.3 Design Considerations for IPv6 9.4 Summary 9.0

3 Presentation_ID 3 © 2008 Cisco Systems, Inc. All rights reserved.Cisco Confidential Chapter 9: Objectives  Explain why routing is necessary for hosts on different networks to communicate.  Describe IP as a communication protocol used to identify a single device on a network.  Given a network and a subnet mask, calculate the number of host addresses available.  Calculate the necessary subnet mask in order to accommodate the requirements of a network.  Describe the benefits of variable length subnet masking (VLSM)  Explain how IPv6 address assignments are implemented in a business network. 9.0.1.1

4 Presentation_ID 4 © 2008 Cisco Systems, Inc. All rights reserved.Cisco Confidential Introduction Subletting IP Networks 9.0.1.2 Consider doing class activity 9.0.1.2 Activity - Call Me

5 Presentation_ID 5 © 2008 Cisco Systems, Inc. All rights reserved.Cisco Confidential Network Segmentation Reasons for Subnetting Large networks need to be segmented into smaller sub-networks, creating smaller groups of devices and services in order to:  Control traffic by containing broadcast traffic within subnetwork  Reduce overall network traffic and improve network performance Subnetting - process of segmenting a network into multiple smaller network spaces called subnetworks or Subnets. Communication Between Subnets  A router is necessary for devices on different networks and subnets to communicate.  Each router interface must have an IPv4 host address that belongs to the network or subnet that the router interface is connected to.  Devices on a network and subnet use the router interface attached to their LAN as their default gateway. 9.1.1.1

6 Presentation_ID 6 © 2008 Cisco Systems, Inc. All rights reserved.Cisco Confidential Why Subnet Networks Communication Between Subnets To determine if traffic is local or remote, the router uses the subnet mask. Each subnet is treated as a separate network space. Devices on the same subnet must use an address, subnet mask, and default gateway 9.1.1.2

7 Presentation_ID 7 © 2008 Cisco Systems, Inc. All rights reserved.Cisco Confidential Subnetting an IPv4 Network IP Subnetting is FUNdamental 9.1.2.1

8 Presentation_ID 8 © 2008 Cisco Systems, Inc. All rights reserved.Cisco Confidential Subnetting an IPv4 Network The Plan – Address Assignment 9.1.2.2  255.0.0.08 network bit, 24 host bits 2^24 = 16,777,216 possible hosts  255.255.0.016 network bit, 16 host bits 2^24 = 65,536 possible hosts  255.255.255.024 network bit, 8 host bits 2^8 = 256 possible hosts  Problem: Our Public IP address is 165.15.0.0/16 We have one network that can hold 65,535 hosts! We need many networks, not one huge one!

9 Presentation_ID 9 © 2008 Cisco Systems, Inc. All rights reserved.Cisco Confidential Subnetting an IPv4 Network Basic Subnetting  Borrowing Bits to Create Subnets  Borrowing 1 bit 2 1 = 2 subnets Subnet 1 Network 192.168.1.128-255/25 Mask: 255.255.255.128 Subnet 0 Network 192.168.1.0-127/25 Mask: 255.255.255.128 Borrowing 1 Bit from the host portion creates 2 subnets with the same subnet mask 9.1.3.1 Do the buttons on 9.1.3.1

10 Presentation_ID 10 © 2008 Cisco Systems, Inc. All rights reserved.Cisco Confidential Subnetting an IPv4 Network Subnets in Use Subnet 0 Network 192.168.1.0-127/25 Subnet 1 Network 192.168.1.128-255/25 9.1.3.2 Do the buttons on 9.1.3.2

11 Presentation_ID 11 © 2008 Cisco Systems, Inc. All rights reserved.Cisco Confidential Subnetting an IPv4 Network Subnetting Formulas  Calculate Number of Subnets  Calculate Number of Hosts 9.1.3.3 Do the buttons on 9.1.3.3

12 Presentation_ID 12 © 2008 Cisco Systems, Inc. All rights reserved.Cisco Confidential Subnetting an IPv4 Network Creating 4 Subnets  Borrowing 2 bits to create 4 subnets. 2 2 = 4 subnets 9.1.3.4 Do the buttons on 9.1.3.4

13 Presentation_ID 13 © 2008 Cisco Systems, Inc. All rights reserved.Cisco Confidential Subnetting an IPv4 Network Creating 8 Subnets  Borrowing 3 bits to Create 8 Subnets. 2 3 = 8 subnets 9.1.3.5 Do the buttons on 9.1.3.5

14 Presentation_ID 14 © 2008 Cisco Systems, Inc. All rights reserved.Cisco Confidential Subnetting an IPv4 Network Creating 8 Subnets(continued) 9.1.3.5 Do the buttons on 9.1.3.5

15 Presentation_ID 15 © 2008 Cisco Systems, Inc. All rights reserved.Cisco Confidential Subnetting an IPv4 Network Creating 8 Subnets(continued) 9.1.3.5 Do the buttons on 9.1.3.5

16 Presentation_ID 16 © 2008 Cisco Systems, Inc. All rights reserved.Cisco Confidential Subnetting an IPv4 Network Creating 8 Subnets(continued) 9.1.3.5 Do the buttons on 9.1.3.5

17 Presentation_ID 17 © 2008 Cisco Systems, Inc. All rights reserved.Cisco Confidential Subnetting an IPv4 Network 9.1.3.6 Activity - Determining the Network Address – Basic 9.1.3.7 Activity - Calculate the Number of Hosts – Basic 9.1.3.8 Activity - Determining the Valid Addresses for Hosts – Basics 9.1.3.9 Activity - Calculate the Subnet Mask 9.1.3.6 Do Activities 9.1.3.6, 9.1.3.7, 9.1.3.8 and 9.1.3.9 in class Students should practice this until mastery.

18 Presentation_ID 18 © 2008 Cisco Systems, Inc. All rights reserved.Cisco Confidential Subnetting an IPv4 Network Creating 100 Subnets with a /16 prefix 9.1.3.10 In situations where more hosts are required, You must borrow bits from the 3 rd octet instead of the 4 th. In this example we have 9 host bits for 510 hosts (2^9 -2)

19 Presentation_ID 19 © 2008 Cisco Systems, Inc. All rights reserved.Cisco Confidential Subnetting an IPv4 Network 9.1.3.11 Calculating the Hosts 9.1.3.11 Do the buttons on 9.1.3.11

20 Presentation_ID 20 © 2008 Cisco Systems, Inc. All rights reserved.Cisco Confidential Subnetting an IPv4 Network 9.1.3.12 Calculating the Hosts 9.1.3.12 Do the buttons on 9.1.3.12

21 Presentation_ID 21 © 2008 Cisco Systems, Inc. All rights reserved.Cisco Confidential Subnetting an IPv4 Network 9.1.3.13 Activity - Determining the Network Address – Advanced 9.1.3.14 Activity - Calculating the Number of Hosts – Advanced 9.1.3.15 Activity - Determining the Valid Addresses for Hosts - Advanced 9.1.3.13 – 9.1.3.15 Do activities 9.1.3.13, 14, 15 in class

22 Presentation_ID 22 © 2008 Cisco Systems, Inc. All rights reserved.Cisco Confidential Determining the Subnet Mask Subnetting Based on Host Requirements There are two considerations when planning subnets:  Number of Subnets required  Number of Host addresses required  Formula to determine number of useable hosts 2^n-2 2^n (where n is the number the number of host bits remaining) is used to calculate the number of hosts -2 Subnetwork ID and broadcast address cannot be used on each subnet 9.1.4.1 Do animation on 9.1.4.1

23 Presentation_ID 23 © 2008 Cisco Systems, Inc. All rights reserved.Cisco Confidential Determining the Subnet Mask Subnetting Network-Based Requirements Calculate number of subnets  Formula 2^n (where n is the number of bits borrowed)  Subnet needed for each department in graphic 9.1.4.2

24 Presentation_ID 24 © 2008 Cisco Systems, Inc. All rights reserved.Cisco Confidential Determining the Subnet Mask Subnetting To Meet Network Requirements  It is important to balance the number of subnets needed and the number of hosts required for the largest subnet.  Design the addressing scheme to accommodate the maximum number of hosts for each subnet.  Allow for growth in each subnet. 9.1.4.3 Do the buttons on 9.1.4.3

25 Presentation_ID 25 © 2008 Cisco Systems, Inc. All rights reserved.Cisco Confidential Determining the Subnet Mask Subnetting To Meet Network Requirements (cont) 9.1.4.4 Do the buttons on 9.1.4.4

26 Presentation_ID 26 © 2008 Cisco Systems, Inc. All rights reserved.Cisco Confidential Benefits of Variable Length Subnet Masking Traditional Subnetting Wastes Addresses  Traditional subnetting - same number of addresses is allocated for each subnet.  Subnets that require fewer addresses have unused (wasted) addresses. For example, WAN links only need 2 addresses.  Variable Length Subnet Mask (VLSM) or subnetting a subnet provides more efficient use of addresses. 9.1.4.4

27 Presentation_ID 27 © 2008 Cisco Systems, Inc. All rights reserved.Cisco Confidential Subnetting an IPv4 Network 9.1.4.5 Activity - Determining the Number of Bits to Borrow Do activities 9.1.4.5 9.1.4.5

28 Presentation_ID 28 © 2008 Cisco Systems, Inc. All rights reserved.Cisco Confidential Benefits of Variable Length Subnet Masking Variable Length Subnet Masks (VLSM)  VLSM allows a network space to be divided in unequal parts.  Subnet mask will vary depending on how many bits have been borrowed for a particular subnet.  Network is first subnetted, and then the subnets are subnetted again.  Process repeated as necessary to create subnets of various sizes. 9.1.5.1 Do buttons on 9.1.5.1

29 Presentation_ID 29 © 2008 Cisco Systems, Inc. All rights reserved.Cisco Confidential Benefits of Variable Length Subnet Masking Basic VLSM 9.1.5.2 Do buttons on 9.1.5.2

30 Presentation_ID 30 © 2008 Cisco Systems, Inc. All rights reserved.Cisco Confidential Benefits of Variable Length Subnet Masking Basic VLSM 9.1.5.3 Do buttons on 9.1.5.3

31 Presentation_ID 31 © 2008 Cisco Systems, Inc. All rights reserved.Cisco Confidential Benefits of Variable Length Subnet Masking VLSM in Practice  Using VLSM subnets, the LAN and WAN segments in example below can be addressed with minimum waste.  Each LANs will be assigned a subnet with /27 mask.  Each WAN link will be assigned a subnet with /30 mask. 9.1.5.4 Do buttons on 9.1.5.4

32 Presentation_ID 32 © 2008 Cisco Systems, Inc. All rights reserved.Cisco Confidential Benefits of Variable Length Subnet Masking VLSM Chart 9.1.5.5 Do buttons on 9.1.5.5

33 Presentation_ID 33 © 2008 Cisco Systems, Inc. All rights reserved.Cisco Confidential Subnetting an IPv4 Network 9.1.5.6 Activity - Practicing VLSM Do activities 9.1.4.6 in class 9.1.4.6

34 Presentation_ID 34 © 2008 Cisco Systems, Inc. All rights reserved.Cisco Confidential Structured Design Planning to Address the Network Allocation of network addresses should be planned and documented for the purposes of:  Preventing duplication of addresses  Providing and controlling access  Monitoring security and performance Addresses for Clients - usually dynamically assigned using Dynamic Host Configuration Protocol (DHCP) Sample Network Addressing Plan 9.2.1.1

35 Presentation_ID 35 © 2008 Cisco Systems, Inc. All rights reserved.Cisco Confidential Subnetting an IPv6 Network Subnetting Using the Subnet ID An IPv6 Network Space is subnetted to support hierarchical, logical design of the network 9.3.1.1 Do buttons on 9.3.1.1

36 Presentation_ID 36 © 2008 Cisco Systems, Inc. All rights reserved.Cisco Confidential Subnetting an IPv6 Network IPV6 Subnet Allocation 9.3.1.2 Do buttons on 9.3.1.2

37 Presentation_ID 37 © 2008 Cisco Systems, Inc. All rights reserved.Cisco Confidential Subnetting an IPv6 Network Subnetting into the Interface ID IPv6 bits can be borrowed from the interface ID to create additional IPv6 subnets 9.3.1.3

38 Presentation_ID 38 © 2008 Cisco Systems, Inc. All rights reserved.Cisco Confidential Chapter 9: Summary  Process of segmenting a network, by dividing it into to multiple smaller network spaces, is called subnetting.  Subnetting a subnet, or using Variable Length Subnet Mask (VLSM) was designed to avoid wasting addresses.  IPv6 address space is a huge address space so it is subnetted to support the hierarchical, logical design of the network not to conserve addresses.  Size, location, use, and access requirements are all considerations in the address planning process.  IP networks need to be tested to verify connectivity and operational performance. 9.4.1.1

39 Presentation_ID 39 © 2008 Cisco Systems, Inc. All rights reserved.Cisco Confidential Ta Da!


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