Download Chapter 9 - Subnetting IP Networks

Chapter 9: Subnetting
IP Networks
Introduction to Networking
9.0
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Chapter 9
9.1 Subnetting an IPv4 Network
9.2 Addressing Schemes
9.3 Design Considerations for IPv6
9.4 Summary
9.0
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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
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Introduction
Subletting IP Networks
Consider doing class activity
9.0.1.2 Activity - Call Me
9.0.1.2
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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
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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
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Subnetting an IPv4 Network
IP Subnetting is FUNdamental
9.1.2.1
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Subnetting an IPv4 Network
The Plan – Address Assignment
 255.0.0.0
8 network bit, 24 host bits
• 2^24 = 16,777,216 possible hosts
 255.255.0.0
16 network bit, 16 host bits
• 2^24 = 65,536 possible hosts
 255.255.255.0
24 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!
9.1.2.2
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Subnetting an IPv4 Network
Basic Subnetting
 Borrowing Bits to Create Subnets
 Borrowing 1 bit 21 = 2 subnets
Do the buttons on 9.1.3.1
Borrowing 1 Bit from the host portion creates 2 subnets with the same subnet mask
Subnet 0
Subnet 1
Network 192.168.1.0-127/25
Network 192.168.1.128-255/25
Mask: 255.255.255.128
Mask: 255.255.255.128
9.1.3.1
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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
Do the buttons on 9.1.3.2
9.1.3.2
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Subnetting an IPv4 Network
Subnetting Formulas
Calculate Number of Subnets
Calculate Number of Hosts
Do the buttons on 9.1.3.3
9.1.3.3
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Subnetting an IPv4 Network
Creating 4 Subnets
Borrowing 2 bits to create 4 subnets. 22 = 4 subnets
9.1.3.4
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Do the buttons on 9.1.3.4
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Subnetting an IPv4 Network
Creating 8 Subnets
Borrowing 3 bits to Create 8 Subnets. 23 = 8 subnets
9.1.3.5
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Do the buttons on 9.1.3.5
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Subnetting an IPv4 Network
Creating 8 Subnets(continued)
9.1.3.5
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Subnetting an IPv4 Network
Creating 8 Subnets(continued)
9.1.3.5
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Do the buttons on 9.1.3.5
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Subnetting an IPv4 Network
Creating 8 Subnets(continued)
Do the buttons on
9.1.3.5
9.1.3.5
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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
Presentation_ID
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.
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Subnetting an IPv4 Network
Creating 100 Subnets with a /16 prefix
• In situations where
more hosts are
required, You must
borrow bits from the
3rd octet instead of
the 4th.
• In this example we
have 9 host bits for
510 hosts (2^9 -2)
9.1.3.10
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Subnetting an IPv4 Network
9.1.3.11 Calculating the Hosts
9.1.3.11
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Do the buttons on 9.1.3.11
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Subnetting an IPv4 Network
9.1.3.12 Calculating the Hosts
9.1.3.12
Presentation_ID
Do the buttons on 9.1.3.12
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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
Presentation_ID
Do activities 9.1.3.13, 14, 15 in class
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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
Presentation_ID
Do animation on 9.1.4.1
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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
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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.
Do the buttons on 9.1.4.3
9.1.4.3
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Determining the Subnet Mask
Subnetting To Meet Network Requirements (cont)
9.1.4.4
Presentation_ID
Do the buttons on 9.1.4.4
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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
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Subnetting an IPv4 Network
9.1.4.5 Activity - Determining the Number of Bits to Borrow
9.1.4.5
Presentation_ID
Do activities 9.1.4.5
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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
Presentation_ID
Do buttons on 9.1.5.1
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Benefits of Variable Length Subnet Masking
Basic VLSM
9.1.5.2
Presentation_ID
Do buttons on 9.1.5.2
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Benefits of Variable Length Subnet Masking
Basic VLSM
9.1.5.3
Presentation_ID
Do buttons on 9.1.5.3
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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
Presentation_ID
Do buttons on 9.1.5.4
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Benefits of Variable Length Subnet Masking
VLSM Chart
9.1.5.5
Presentation_ID
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Subnetting an IPv4 Network
9.1.5.6 Activity - Practicing VLSM
9.1.4.6
Presentation_ID
Do activities 9.1.4.6 in class
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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
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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
Presentation_ID
Do buttons on 9.3.1.1
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Subnetting an IPv6 Network
IPV6 Subnet Allocation
9.3.1.2
Presentation_ID
Do buttons on 9.3.1.2
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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
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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
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Ta Da!
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