Download Addressing the Network – IPv4 - Information Systems Technology

Addressing the Network
– IPv4
Network Fundamentals – Chapter 6
Sandra Coleman, CCNA, CCAI
Version 4.0
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Objectives

Explain the structure IP addressing and demonstrate the ability
to convert between 8-bit binary and decimal numbers.

Given an IPv4 address, classify by type and describe how it is
used in the network.

Explain how addresses are assigned to networks by ISPs and
within networks by administrators.

Determine the network portion of the host address and explain
the role of the subnet mask in dividing networks.

Given IPv4 addressing information and design criteria, calculate
the appropriate addressing components.

Use common testing utilities to verify and test network
connectivity and operational status of the IP protocol stack on a
host.
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IP Addressing Structure
 Describe an octet, network portion, host portion
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IP Addressing Structure
 Describe these parts of an IPv4 address. Total of 32
bits long!
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IP Addressing Structure
 Practice converting 8-bit binary to decimal – See online
curriculum section 6.1.3 for an online practice tool.
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IP Addressing Structure
 Convert decimal to 8-bit binary
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IP Addressing Structure
 Practice converting decimal to 8-bit binary – Online
curriculum 6.1.5 for online practice tool
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Classify and Define IPv4 Addresses
 Name the three types of addresses in the network and
describe the purpose of each type
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Types of addresses
 Network
The network address is a standard way to refer to a network. For
example, we could refer to the network shown in the figure as "the
10.0.0.0 network.“ All hosts in the 10.0.0.0 network will have the same
network bits (high-order bits). The lowest address is reserved for the
network address. This address has a 0 for each host bit in the host
portion of the address. This is the part routers use to forward packets!
 Broadcast
Special address for each network that allows communication to all the
hosts in that network. To send data to all hosts in a network, a host can
send a single packet that is addressed to the broadcast address of the
network. The broadcast address uses the highest address in the
network range. This is the address in which the bits in the host portion
are all 1s.
 Host
Every end device requires a unique address to deliver a packet to that
host. In IPv4 addresses, we assign the values between the network
address and the broadcast address to the devices in that network.
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Classify and Define IPv4 Addresses
 Determine the network, broadcast and host addresses
for a given address and prefix combination – practice
this…online curriculum section 6.2.2
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Types of networks
 Unicast - the process of sending a packet from one host to an individual
host. This is used for all normal traffic.
 Broadcast - the process of sending a packet from one host to all hosts in
the network. Broadcast transmission is used for the location of special
services/devices for which the address is not known or when a host
needs to provide information to all the hosts on the network.
2 types of broadcast – ROUTERS DO NOT FORWARD BROADCASTS!
Limited - is used for communication that is limited to the hosts on the local
network.
Directed - directed broadcast is sent to all hosts on a specific network.
 Multicast - the process of sending a packet from one host to a selected
group of hosts. Some examples include: Video and audio distribution,
Routing information exchange by routing protocols, Distribution of
software, News feeds
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Classify and Define IPv4 Addresses
 Name the three types of communication in the Network
Layer and describe the characteristics of each type
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Classify and Define IPv4 Addresses
 Identify the address ranges reserved for these special
purposes in the IPv4 protocol
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Private addressing
 Must be unique in the LAN in which they are located
 CAN NOT be routed on the internet. If hosts with a
private address need access to the internet, must use
some form of NAT or PAT (discussed in a later course)
to translate the address to a public address
 The private address blocks are: (KNOW THESE!)
Class A - 10.0.0.0 to 10.255.255.255 (10.0.0.0 /8)
Class B - 172.16.0.0 to 172.31.255.255 (172.16.0.0 /12)
Class C - 192.168.0.0 to 192.168.255.255 (192.168.0.0 /16)
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Public addressing
 The remaining addresses (not in the private address
block range) are designed to access the internet and
carry the user wherever he/she wants to go.
 Some of these addresses are designated for special
purposes.
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Special IP Addresses – can’t be assigned!
 None of these addresses will be forwarded by a router and most
can’t be assigned to a device (Link-local & Test-Net are the
exception to that rule)
1. Network Address – FIRST address of any network
2. Broadcast Address – LAST address of any network
3. Default Route – 0.0.0.0 – 0.255.255.255 – ‘catch-all’ route when a
specific route is NOT available
4. Loopback Addresses – 127.0.0.1 – 127.255.255.255 – used to test
the configuration of TCP/IP on the local host (your NIC) –
bypasses some of the lower layers of TCP/IP stack
5. Link-Local Addresses - 169.254.0.0 to 169.254.255.255 These
addresses can be automatically assigned to the local host by the
OS in environments where no IP configuration is available. I.E.
can’t get DHCP configurations.
6. Test-Net Addresses - 192.0.2.0 to 192.0.2.255 - is set aside for
teaching and learning purposes
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Classify and Define IPv4 Addresses
 See online curriculum 6.2.5 for an online tool
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Classify and Define IPv4 Addresses
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Classify and Define IPv4 Addresses
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Classful Addressing
 Class A – designed to support extremely large networks
with more than 16 million host addresses.
 Class B – designed to support the needs of moderate to
large size networks with more than 65,000 hosts
 Class C – the most commonly available of the historic
address classes. This address space was intended to
provide addresses for small networks with a maximum
of 254 hosts.
 Class D – Multicasting
 Class E – Experimental
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Limits of Classful routing
 Abandoned in the 1990’s
 Assumptions were made about the subnet mask based
on the first octet. This is true of the OS and the routing
protocols
 Wasted address space
If a company needed 260 addresses, they would have to be
assigned a class B address of 65,000 addresses.
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Planning an addressing scheme..WHY?
 Preventing duplication of addresses – keep up with IP
addresses as they are assigned. Duplication is NOT
allowed!
 Providing and controlling access - if a server has a
random address assigned (DHCP), blocking access to its
address is difficult and clients may not be able to locate
this resource. Some devices need not only internal, but
external access (servers, for example)
 Monitoring security and performance - examine network
traffic looking for addresses that are generating or
receiving excessive packets. If we have proper planning
and documentation of the network addressing, we can
identify the device on the network that has a problematic
address.
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Assigning addresses
 Some examples of different types of hosts are:
End devices for users
Servers and peripherals (static addresses, please)
Hosts that are accessible from the Internet
Intermediary devices (static addresses please)
 Each of these different device types should be
allocated to a logical block of addresses within the
address range of the network.
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Address planning..
 Considerations include:
Will there be more devices connected to the network than public
addresses allocated by the network's ISP?
Will the devices need to be accessed from outside the local
network?
If devices that may be assigned private addresses require access to
the Internet, is the network capable of providing a Network Address
Translation (NAT) service?
 If there are more devices than available public addresses
(found a LOT with class C (254 hosts) assignments, only
those devices that will directly access the Internet - such
as web servers - require a public address. A NAT service
would allow those devices with private addresses to
effectively share the remaining public addresses.
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Assigning Addresses
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Static addressing
 The network administrator must manually configure the
network information for a host. At a minimum, this
includes entering the host IP address, subnet mask, and
default gateway.
 Static addresses have some advantages over dynamic
addresses. For instance, they are useful for printers,
servers, and other networking devices that need to be
accessible to clients on the network.
 When using static IP addressing, it is necessary to
maintain an accurate list of the IP address assigned to
each device. These are permanent addresses and are
not normally reused. Typically assigned to servers,
network printers, routers, switches, etc, but NOT to PC’s
(laptop or desktop)
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Assigning Addresses
 Explain how end user devices can obtain addresses
dynamically through DHCP.
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Assigning Addresses
 Explain which types of addresses should be assigned
to devices other than end user devices
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Assigning Public Addresses
 IANA – Internet Assigned Numbers Authority
 IANA gave these out directly until about mid-1990’s.
 All remaining IPv4 were then assigned to RIR’s (Regional
Internet Registries) to maintain and then to start with IPv6
addresses
 ARIN is who your ISP gets its IP address blocks from.
 ARIN (American Registry for Internet Numbers) - North America
Region http://www.arin.net
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Assigning Addresses
 Identify different types of ISPs and their roles in
providing Internet connectivity
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ISP’s
 The farther you get from the internet backbone, services
are
Cheaper
Less reliable
Slower
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IPv6 features
 Larger address space
 Data types and class of service updated
 Uses authentication and encryption
 Why was it developed?
To give us expanded addressing capabilities!
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IPv6
 128 bit addressing in hexadecimal #’s separated by colons
 Simpler header to speed up Tx/Rx speed
 Authentication and Privacy capabilities
 Designed for scalability (ability to grow)
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IPv6 continued…
 IPv6 is not merely a new Layer 3 protocol - it is a new
protocol suite.
 New protocols at various layers of the stack have been
developed to support this new protocol.
 There is a new messaging protocol (ICMPv6) and new
routing protocols.
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Determine the network portion of the host address and
the role of the subnet mask
Network
Portion – blue
SN Mask bits
ALL 1’s
Host Portion –
red
SN Mask bits
ALL 0’s
CIDR Notation(Classless Inter Domain Routing –
Prefix /24)
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 ANDing is like multiplying…convert IP and subnet mask
down to binary, multiply them together..get a binary
result…convert back to decimal.
 This is what routers DO!!!
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 Use ANDing logic to determine an outcome
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 Observe the steps in the ANDing of an IPv4 host address
and subnet mask..online curriculum 6.4.3
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Calculating Addresses
 Use the subnet mask to divide a network into smaller
networks
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Powers of 2
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Calculating a Subnet
 We will subnet the IP address:
223.14.17.0
 What class IP address is this?
Class C
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Step #1
 Determine the default subnet mask
 Class C default subnet mask:
255.255.255.0
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Step #2
 Determine the number of subnets needed and hosts
needed on each to determine how many bits to borrow
from the host ID.
 Need:
13 subnets
10 hosts on each subnet
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Step #3
 Figure the actual number of subnets and hosts
by borrowing bits from host ID.
 Let’s see how many subnets and hosts we will
have by borrowing 4 bits from the host.
 2bb= possible subnets
 2br = possible hosts
 2br – 2 = usable hosts
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Step #3 continued…
223.14.17.0
XXXX
2bb=16
possible
subnets
HHHH
2br=16 possible
hosts for each
subnet
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Step #3 continued…
 We get 16 possible subnets and 16 possible hosts
for each subnet because:
For the 4 bits borrowed each bit can be a 1 or a 0 leaving
you with 24 or 16 possible combinations.
The same goes for the 4 leftover host bits.
 Important: There are only 14 available hosts on
each subnet. Why?
 Because you cannot use the first and last address
within each subnet. (No exceptions!)
 For each, one is the broadcast address and one is
the network address.
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Step #4
 Determine the subnet mask.
223.14.17.0
XXXX

HHHH
Where X represents the borrowed bits
for subnetting.
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Step #4 continued…
 Add the place values of X together to get the last octet
decimal value of the subnet mask.
128 + 64 + 32 + 16 = 240
The subnet mask is:
255.255.255.240
 The subnet mask is used to reveal
the subnet and host address fields
in IP addresses.

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Step 5
 Determine the ranges of host addresses for each
subnet.
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Step 5 continued…
Subnet #
Subnet Bits Host Bits
In Decimal
1
0000
0000-1111
.0 -.15
2
0001
0000-1111
.16 - .31
3
0010
0000-1111
.32 - .47
4
0011
0000-1111
.48 - .63
5
0100
0000-1111
.64 - .79
6
0101
0000-1111
.80 - .95
7
0110
0000-1111
.96 - .111
8
0111
0000-1111 .112 - .127
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Step 5 continued…
Subnet #
Subnet Bits Host Bits
In Decimal
9
1000
0000-1111
10
1001
0000-1111 .144 - .159
11
1010
0000-1111 .160 - .175
12
1011
0000-1111 .176 - .191
13
1100
0000-1111 .192 - .207
14
1101
0000-1111 .208 - .223
15
1110
0000-1111 .224 - .239
16
1111
0000-1111 .240 - .255
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VLSM…not wasting IP addresses..
 Extract network addresses from host addresses using
the subnet mask. MUST know how to do this!
 Always start with the largest block and work down!
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VLSM– Know THIS!
 Calculate the number of hosts in a network range given
an address and subnet mask
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 Given a subnet address and subnet mask, calculate the
network address, host addresses and broadcast
address (6.5.4) MUST DO THIS!
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Calculating Addresses
 Given a pool of addresses and masks, assign a host
parameter with address, mask and gateway (6.5.5)
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Calculating Addresses
 Given a diagram of a multi-layered network, address
range, number of hosts in each network and the ranges
for each network, create a network scheme that
assigns addressing ranges to each network (6.5.6)
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Which one of the following are valid
HOST addresses?
 192.168.12.127/26
 172.31.5.155/26
 172.31.5.193/26
 192.168.6.95/27
 192.168.5.159/27
 192.168.5.207/27
 Be able to do this on your test!
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Testing the Network Layer
 Use the ping command to determine if the IP protocol is
operational on a local host (127.0.0.1). If this fails,
TCP/IP is not properly installed on the host!
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Testing the Network Layer
 Use ping to verify that a local host can communicate
with a gateway across a local area network
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Testing the Network Layer
 Use ping to verify that a local host can communicate via
a gateway to a device in remote network
Remember, many network
administrators limit or prohibit the
entry of ICMP datagrams into the
corporate network. Therefore, the
lack of a ping response could be
due to security restrictions and
not because of non-operational
elements of the networks.
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Testing the Network Layer
 Use tracert/traceroute to observe the path between two
devices as they communicate and trace the steps of
tracert/traceroute's operation
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Testing the Network Layer
 ICMP – provides control and error messages to the
TCP/IP protocol suite.
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ICMP messages
 If the TTL mechanism expires before a packet reaches
its destination, what happens?
The router DROPS the packet
Sends an ICMP ‘Time Exceeded’ message back to the source!
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1.
2.
3.
4.
5.
6.
7.
WOW…are you okay? Still with me? 
You MUST learn how to do this.
It will be part of your hands-on finals
NO CALCULATORS ALLOWED on this test or the
CCNA!
Practice….Practice…… Practice….That’s the only
way to get this to stick with you.
Test – TBD
Online Test - TBD
Study Guide:
1.
2.
3.
4.
Pg. 152 – ALL of it
Pg. 155 – Binary Matching exercise
Pg. 156 – Concept Questions
Pg. 157-158 – Concept Questions
8. Activities – 6-1, 6-2 – pg. 178, pg. 183
9. We have several handouts, I’ve posted some of them
on the WEB so that if you lose yours, you can print
yourself another one.
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