Chapter 6 IPv4 Addresses – Part 2

Chapter 6IPv4 Addresses – Part 2

CIS 81 Networking Fundamentals

Rick Graziani

Cabrillo College

[email protected]

Last Updated: 3/30/2008

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This Presentation

For a copy of this presentation and access to my web site for other CCNA, CCNP, and Wireless resources please email me for a username and password. Email: [email protected] Web Site: www.cabrillo.edu/~rgraziani

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Note

This presentation is not in the order of the book or online curriculum. This presentation also contains information beyond the curriculum.

Host IP Addresses

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Host IP Addresses

172.0.0.0 (net) 10101100.00000000.00000000.00000000

255.0.0.0 (SM)11111111.00000000.00000000.00000000

172.0.0.1 10101100.00000000.00000000.00000001

172.255.255.254 10101100.11111111.11111111.11111110

172.255.255.255 10101100.11111111.11111111.11111111

(broadcast)

172.16.0.0 (net) 10101100.00010000.00000000.00000000

255.255.0.0 (SM) 11111111.11111111.00000000.00000000

172.16.0.1 10101100.00010000.00000000.00000001

172.16.255.25410101100.00010000.11111111.11111110

172.16.255.25510101100.00010000.11111111.11111111

(broadcast)

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Host IP Addresses

172.1.16.0 10101100.00000001.00010000.00000000

255.255.240.0 11111111.11111111.11110000.00000000

172.1.16.1 10101100.00000001.00010000.00000001

…

172.1.31.254 10101100.00000001.00011111.11111110

172.1.31.255 10101100.00000001.00011111.11111111

(broadcast)

Number of hosts: 212 – 2 = 4,096 – 2 = 4,094 hosts

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Who assigns IP Network Addresses?

Internet Assigned Numbers Authority (IANA) (http://www.iana.net) is the master holder of the IP addresses.

Today, the remaining IPv4 address space has been allocated to various other registries to manage for particular purposes or for regional areas. Regional Internet Registries (RIRs)

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Regional Internet Registries (RIR)

The 5 RIR’s are: AfriNIC (African Network Information Centre) - Africa Region

http://www.afrinic.net APNIC (Asia Pacific Network Information Centre) - Asia/Pacific Region

http://www.apnic.net ARIN (American Registry for Internet Numbers) - North America Region

http://www.arin.net LACNIC (Regional Latin-American and Caribbean IP Address Registry) -

Latin America and some Caribbean Islands http://www.lacnic.net RIPE NCC (Reseaux IP Europeans) - Europe, the Middle East, and Central

Asia http://www.ripe.net

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ISP (Internet Service Providers)

Tier 1 ISP: Large national or international ISPs that are directly connected to the

Internet backbone. Customers of Tier 1 ISPs:

lower-tiered ISPs large companies and organizations.

Offer reliability and speed AOL, SPRINT, Global Crossing, AT&T, Level 3, Verizon, NTT, Quest,

SAVVIS

Most companies or organizations obtain their IPv4 address blocks from an ISP.

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Tier 2 ISP: Acquire their Internet service from Tier 1 ISPs. Tier 2 ISPs generally

focus on business customers. Examples: Allstream, AboveNet, British Telecom, Cogent

Communications, France Telecom, Teleglobe TeliaSonera International Carrier Time Warner Telecom, Tiscali International Network, XO Communications


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Tier 3 ISP: Purchase their Internet service from Tier 2 ISPs. The focus of these

ISPs is the retail and home markets in a specific locale. Examples: Local ISPs


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Special Unicast IPv4 Addresses

Default Route

Loopback Address Special address that hosts use to direct traffic to themselves. 127.0.0.0 to 127.255.255.255

Link-Local Addresses 169.254.0.0 to 169.254.255.255 (169.254.0.0 /16) Can be automatically assigned to the local host by the operating system

in environments where no IP configuration is available.

TEST-NET Addresses 192.0.2.0 to 192.0.2.255 (192.0.2.0 /24) Set aside for teaching and learning purposes. These addresses can be used in documentation and network examples.

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Private IP Addresses

RFC 1918 10.0.0.0 to 10.255.255.255 (10.0.0.0 /8) 172.16.0.0 to 172.31.255.255 (172.16.0.0 /12) 192.168.0.0 to 192.168.255.255 (192.168.0.0 /16)

The addresses will not be routed in the Internet Need NAT/PAT (next)

Should be blocked by your ISP Allows for any network to have up to 16,777,216 hosts (/8)

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Introducing NAT and PAT

NAT is designed to conserve IP addresses and enable networks to use private IP addresses on internal networks.

These private, internal addresses are translated to routable, public addresses.

IPv4 addresses are almost depleted. NAT/PAT has allowed IPv4 to be the predominant network protocol, keeping

IPv6 at-bay (for now).

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NAT Example

128.23.2.2 10.0.0.3 .... Data

DA SA

IP Header

128.23.2.2 179.9.8.80 .... Data

DA SA

IP Header

The translation from Private source IP address to Public source IP address.

1 2

1 2

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NAT Example

Translation back, from Public destination IP address to Private destination IP address.

179.9.8.80 128.23.2.2 .... Data

DA SA

IP Header

10.0.0.3 128.23.2.2 .... Data

DA SA

IP Header

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PAT Example

128.23.2.2 10.0.0.3 80 1331 Data

DA SA

IP Header

DP SP

TCP/UDPHeader

128.23.2.2 10.0.0.2 80 1555 Data

DA SA

IP Header

DP SP

TCP/UDPHeader

128.23.2.2 179.9.8.80 80 3333 Data

DA SA

IP Header

DP SP

TCP/UDPHeader

128.23.2.2 179.9.8.80 80 2222 Data

DA SA

IP Header

DP SP

TCP/UDPHeader

NAT/PAT table maintains translation of:

DA, SA, SP

1 2

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PAT Example

179.9.8.80 128.23.2.2 3333 80 Data

DA SA

IP Header

DP SP

TCP/UDPHeader

179.9.8.80 128.23.2.2 2222 80 Data

DA SA

IP Header

DP SP

TCP/UDPHeader

10.0.0.3 128.23.2.2 1331 80 Data

DA SA

IP Header

DP SP

TCP/UDPHeader

10.0.0.2 128.23.2.2 1555 80 Data

DA SA

IP Header

DP SP

TCP/UDPHeader

4 3

NAT/PAT table maintains translation of:

SA (DA), DA (SA), DP (SP)

The Subnet Mask and the AND Operation

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Subnet Mask

The subnet mask is used to separate the network portion from the host portion of the address.

On a host, the subnet mask tells the host what network it belongs to. Why does a host need to know what network it belongs to?

Host: “I’m a host on the 192.168.1.0/24 network.”

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Subnet Mask

Why does a host need to know what network it belongs to? So, it knows whether to encapsulate the IP packet into an Ethernet

frame with: The Destination MAC Address of the default gateway

Must know the default gateway’s IP address The Destination MAC Address of the host with the Destination IP

address of the packet Later when we discuss Ethernet

Host: “I’m a host on the 192.168.1.0/24 network.”

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Subnet Mask

Devices such as hosts use the bit-wise AND operation on the: Host IP address Subnet mask

AND operation: 1 AND 1 = 1 0 AND anything = 0

Host IP: 172.16.33.10 10101100.00010000.00100001.00001010

Mask: 255.255.0.0 11111111.11111111.00000000.00000000

-----------------------------------

Net Add: 172.16.0.0 10101100.00010000.00000000.00000000

Network Host

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Subnet Mask


Host IP: 172.16.33.10 10101100.00010000.00100001.00001010

Mask: 255.255.255.0 11111111.11111111.11111111.00000000

-----------------------------------

Net Add: 172.16.33.0 10101100.00010000.00100001.00000000

Network Host

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Subnet Mask


Host IP: 172.1.17.9 10101100.00000001.00010001.00001001

Mask: 255.255.240.0 11111111.11111111.11110000.00000000

-----------------------------------

Net Add: 172.1.16.0 10101100.00000001.00010000.00000000

Network Host

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Subnet Masks: Non-Natural Boundaries

Subnet masks do not have to end on natural octet boundaries

172.1.16.0 10101100.00000001.00010000.00000000

255.255.240.0 11111111.11111111.11110000.00000000

172.1.16.1 10101100.00000001.00010000.00000001

…

172.1.31.254 10101100.00000001.00011111.11111110

172.1.31.255 10101100.00000001.00011111.11111111

(broadcast)

Number of hosts: 212 – 2 = 4,096 – 2 = 4,094 hosts

Subnetting: First Look

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Subnets and Subnet Masks

Formalized in 1985, the subnet mask breaks a single network in to smaller pieces.

Allows network administrators to divide their network into small networks or subnets.

Advantages will be discussed later.

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What is subnetting?

Subnetting is the process of borrowing bits from the HOST bits, in order to divide the larger network into small subnets.

Subnetting does NOT give you more hosts, but actually costs you hosts. You lose two host IP Addresses for each subnet, one for the subnet IP address

and one for the subnet broadcast IP address. You lose the last subnet and all of it’s hosts’ IP addresses as the broadcast for

that subnet is the same as the broadcast for the network. In older technology, you would have lost the first subnet, as the subnet IP

address is the same as the network IP address. (This subnet can be used in most networks.)

Network Network Host Host

172 16 0 0

Network Network Subnet Host

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AnalogyBefore subnetting: In any network (or subnet) we can not use

all the IP addresses for host addresses. We lose two addresses for every network

or subnet.1. Network Address - One address is reserved

to that of the network. For Example: 172.16.0.0 /16

2. Broadcast Address – One address is reserved to address all hosts in that network or subnet. For Example: 172.16.255.255

This gives us a total of 65,534 usable hosts

98 Apples (100 – 2)

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Analogy

It is the same as taking a barrel of 100 apples and dividing it into 10 barrels of 10 apples each.

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10

10

1010

10

10

10

10

10

10 barrels x 10 apples = 100 apples

98 Apples (100 – 2)

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However, in subnetting we will see that we lose two apples per subnet: one for the network address one for the broadcast address

(less 2) (less 2) (less 2)



8 8 8

8 8 8

8 8 8

8


2 = 1 network address + 1 broadcast address

98 Apples (100 – 2)

(less 2)

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In legacy networks, we also lost: The first basket (subnet)

The network address of the first subnet is the network address of the entire network

The last basket (subnet) The broadcast address for the last subnet is the

same as for the entire network.




8 8 8

8 8 8

8 8 8

8


2 = 1 network address + 1 broadcast address

98 Apples (100 – 2)

(less 2)

X

X

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Subnet Example

Network Network Subnet Host

Network address 172.16.0.0 with /16 Base Network Mask

172 16 0 0

172 16 1 0

172 16 2 0

Using Subnets: Subnet Mask 255.255.255.0 or /24

172 16 3 0

172 16 Etc. 0

172 16 254 0

172 16 255 0

256 Subnets

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Subnets Addresses

Subnet addresses: All 0’s in host portion

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Subnet Example

Network Network Subnet Hosts

172 16 0 1

172 16 1 1

172 16 2 1

172 16 3 1

172 16 Etc. 1

172 16 254 1

172 16 255 1

Each subnet has 254 hosts, 28 – 2

254

254

254

254

254

254

Broadcast

Network address 172.16.0.0 with /16 Base Network Mask

Using Subnets: Subnet Mask 255.255.255.0 or /24

255

255

255

255

255

255

254 255

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With NO subnetting:

Network First Host Last Host Broadcast

172.16.0.0 172.16.0.1 172.16.255.254 172.16.255.255

65,534 host addresses, one for network address and one for broadcast address.

Host IP Address: 172.16.3.50 A host of the 172.16.0.0 /16 network


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With subnetting:

Network First Host Last Host Broadcast

172.16.0.0 172.16.0.1 172.16.0.254 172.16.0.255

172.16.1.0 172.16.1.1 172.16.1.254 172.16.1.255

172.16.2.0 172.16.2.1 172.16.2.254 172.16.2.255

172.16.3.0 172.16.3.1 172.16.3.254 172.16.3.255

172.16.4.0 172.16.4.1 172.16.4.254 172.16.4.255

172.16.5.0 172.16.5.1 172.16.5.254 172.16.5.255

172.16.6.0 172.16.6.1 172.16.6.254 172.16.6.255

172.16.7.0 172.16.7.1 172.16.7.254 172.16.7.255

…

172.16.254.0 172.16.254.1 172.16.254.254 172.16.15.255

172.16.255.0 172.16.255.1 172.16.255.254 172.16.255.255


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With subnetting:Network First Host Last Host Broadcast

Hosts

172.16.0.0 172.16.0.1 172.16.0.254 172.16.0.255 254

172.16.1.0 172.16.1.1 172.16.1.254 172.16.1.255 254

172.16.2.0 172.16.2.1 172.16.2.254 172.16.2.255 254

172.16.3.0 172.16.3.1 172.16.3.254 172.16.3.255 254

172.16.4.0 172.16.4.1 172.16.4.254 172.16.4.255 254

172.16.5.0 172.16.5.1 172.16.5.254 172.16.5.255 254

172.16.6.0 172.16.6.1 172.16.6.254 172.16.6.255 254

172.16.7.0 172.16.7.1 172.16.7.254 172.16.7.255 254

…

172.16.254.0 172.16.254.1 172.16.254.254 172.16.15.255 254

172.16.255.0 172.16.255.1 172.16.255.254 172.16.255.255 254 ---

65,024

Total address = 256 subnets * (256 hosts – 2)

= 256 * 254

= 65,024

NOTE: It is common for some network administrator to not use the last subnet.

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With subnetting:Network First Host Last Host Broadcast

172.16.0.0 172.16.0.1 172.16.0.254 172.16.0.255

172.16.255.0 172.16.255.1 172.16.255.254 172.16.255.255

Major Network Address: 172.16.0.0

Major Network Mask: 255.255.0.0

Major Network Broadcast Address: 172.16.255.255

Subnet Mask: 255.255.255.0

First Subnet:

Subnet Address: 172.16.0.0

Subnet Broadcast Address: 172.16.0.255

Last Subnet:

Subnet Address: 172.16.255.0

Subnet Broadcast Address: 172.16.255.255

Subnetting: Step-by-step

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Determining Network and Subnet Information

Use the Classless Subnetting Worksheet (Excel Spreadsheet) to do the following:

Given any IP address and major network mask we can determine: Major Network Address First host address of the network Last host address of the network Broadcast address of the network Number of usable hosts in the network

If the network is subnetted and we know the subnet mask we can determine: Subnet (network) Address First host address of the subnet Last host address of the subnet Broadcast address of the subnet Number of usable hosts in the subnet Number of usable subnets in this network

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See these spreadsheets on my website

Worksheet: Classless Subnetting Worksheet (Excel spreadsheet)

Nutshell: Classless Subnetting in a Nutshell (Excel spreadsheet)

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Part 1: Determine Major Network Information

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Convert IP Address/Network Mask to Binary

First, let’s determine the Major Network Information. This is the information for the entire network, whether or not there are subnets. Using the Major Network Mask, determine the major network Address, the broadcast

address for the entire network, and the number of hosts for the entire network. The Major Network Mask (or Base Mask, Subnet Mask) is provided by the ISP. Convert these addresses to binary.

Host IP Address:138.101.114.250Major Network Mask: 255.255.0.0 (/16)

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Determine Network Address

Determine the Network Address by using the AND operation. Perform a bit-wise AND operation on the IP Address and the Subnet Mask Note: 1 AND 1 results in a 1, 0 AND anything results in a 0 Express the result in Dotted Decimal Notation The result is the Major Network Address of this for this host IP Address is

138.101.0.0

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Determine Network Address A simple way of doing the AND operation:1. In the Network mask locate where the 1’s end and the 0’s begin and draw a line. (I

call this the “Major Network Divide” or “MD” on the worksheet.)2. Now copy all of the bits above the 1 bits in the Network mask, to the Network

address.3. For the rest of the bits in the Network address (the bits below the 0’s in the Network

mask) write all 0’s.

Network Portion Host Portion

Copy the bits from the Host IP Address to the Major Network Address

Write all 0’s below the 0’s in the Major Network Mask

MD

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Network: Determine First Host, Last Host, Broadcast Addresses Remember that the network mask separates the network portion of the address from

the host portion. Major Network Mask: 255.255.0.0 or /16

The network address has all 0’s in the host portion of the address The broadcast address has all 1’s in the host portion of the address The first host is all 0’s and a 1 in the host portion of the address. The last host is all 1’s and a 0 in the host portion of the address.


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Network: Determine First Host, Last Host, Broadcast Addresses The network address has all 0’s in the host portion of the address The broadcast address has all 1’s in the host portion of the address The first host is all 0’s and a 1 in the host portion of the address. The last host is all 1’s and a 0 in the host portion of the address.


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Network: Determine the number of usable hosts By counting the number of host bits we can determine the total number of usable hosts for this

network (before subnetting).Host bits: 16Total number of hosts:

216 = 65,53665,536 – 2 = 65,534 (Can’t use the all 0’s address, network address, or the all 1’s address, broadcast address.)

Host Portion = 16 bitsNetwork Portion

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Part 2: Determine Subnet Information

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Convert IP Address/Subnet Mask to Binary Now we will determine the Subnet Network Information. (Assuming we are subnetted.) This is the information only for that subnet. Using the Subnet Mask, determine the Subnet Address, the broadcast address for the entire network, and the number of hosts for the subnet. The Subnet Mask is determined by the network administrator, depending upon the number of subnets and the number of hosts per subnet that

are needed. Convert these addresses to binary.

Host IP Address: 138.101.114.250Subnet Mask: 255.255.255.192 (/26)

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Determine Subnet Address Determine the Network Address by using the AND operation. Perform a bit-wise AND operation on the IP Address and the Subnet Mask Note: 1 AND 1 results in a 1, 0 AND anything results in a 0 Express the result in Dotted Decimal Notation The result is the Major Network Address of this for this host IP Address is

138.101.114.192

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Determine Subnet Address A simple way of doing the AND operation:1. In the Subnet mask locate where the 1’s end and the 0’s begin and draw a line. (I call this the “Subnet

Divide” or “SD” on the worksheet.)2. Now copy all of the bits above the 1 bits in the Subnet mask, to the Network address.3. For the rest of the bits in the Subnet address (the bits below the 0’s in the Network mask) write all 0’s.

Network/Subnet Portion Host Portion

Copy the bits from the Host IP Address to the Major Network Address Write all 0’s below the 0’s in

the Major Network Mask

SD

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Subnet: Determine First Host, Last Host, Broadcast Addresses Remember that the network mask separates the network portion of the address from

the host portion. Subnet Mask: 255.255.255.192 or /26

The network address has all 0’s in the host portion of the address The broadcast address has all 1’s in the host portion of the address The first host is all 0’s and a 1 in the host portion of the address. The last host is all 1’s and a 0 in the host portion of the address.

Network PortionHost Portion

Subnet Portion

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Subnet: Determine First Host, Last Host, Broadcast Addresses The subnet address has all 0’s in the host portion of the subnet address The broadcast address has all 1’s in the host portion of the subnet address The first host is all 0’s and a 1 in the host portion of the subnet address. The last host is all 1’s and a 0 in the host portion of the subnet address.


Subnet Portion

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Subnet: Determine the number of usable hosts By counting the number of host bits we can determine the total number of usable hosts for this

subnet.Host bits: 6Total number of hosts:

26 = 6464 – 2 = 62 (Can’t use the all 0’s address, network address, or the all 1’s address, broadcast address.)


SD

Subnet Portion

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Subnet: Determine the number of usable subnets By counting the number of subnet bits we can determine the total number of usable hosts for

this subnet.Subnet bits: 10Total number of hosts:

210 = 1,0241,024 – (0, 1, or 2) = ? 1,024 – 1 = 1,023 usable subnets

The number of usable subnets depends upon whether or not we can use the first and/or last subnets. In today’s networks, both the first and last subnets are generally usable.

In this example, the network administrator has determined the last subnet is not to be used.


Subnet Portion

SDMD

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Overall Visual The subnet address has all 0’s in the host portion of the subnet address The broadcast address has all 1’s in the host portion of the subnet address The first host is all 0’s and a 1 in the host portion of the subnet address. The last host is all 1’s and a 0 in the host portion of the subnet address.

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Overall VisualThe following information must be provided: IP Address (host or network) Major Network MaskIf subnetted: Subnet Mask Number of usable subnets (less 0, 1, or 2)

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NotesQuick check First host: 1 more than network/subnet address Last host: 1 less than broadcast Does the host IP address fall in the range of network host

addresses? Of subnet host addresses?

How do hosts view the network? Hosts receive a host IP address and mask. Hosts only see themselves as part of their subnet (or network if not

subnetted). They don’t know or care if they are in a network or subnet. Almost all networks are a subnet of some larger network.

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See these spreadsheets on my website

Worksheet: Classless Subnetting Worksheet (Excel spreadsheet)

Nutshell: Classless Subnetting in a Nutshell (Excel spreadsheet)

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Tips

Use worksheets Don’t do short-cuts unless you understand the process we just

discussed and you know what you are doing. Only use a subnet calculator to check your answers.

You must know how to subnet, then you can use the calculator. Interviews, exams, and certification exams do not allow subnet

calculators. Practice, practice, practice!

Chapter 6IPv4 Addresses – Part 2

CIS 81 Networking Fundamentals

Rick Graziani

Cabrillo College

[email protected]

Last Updated: 3/30/2008

Documents

Chapter 6 IPv4 Addresses – Part 2