1. CPMT 1449 Computer Networking Technology – Lesson 3
CPMT 1449 Computer Networking Technology – Lesson 3.2-Chapter 10 In-Depth TCP/IP Networking

2. Learning Objectives
Understand methods of networking design unique to TCP/IP networks, including subnetting, CIDR, and address translation
Explain the differences between public and private TCP/IP networks
Describe the protocols used between mail clients and mail servers, including SMTP, POP3, IMAP4
Employ multiple TCP/IP utilities for network discovery and troubleshooting

3. Subnetting Subnetting is segmenting networks
There are several reasons to subnet a network
Enhanced security
Improve performance
Simplify troubleshooting
Conserving IP address blocks

4. Classful Addressing in IPv4
Adheres to network class distinctions
An IPv4 address is divided into 2 portions
Network
Host
Class A has 8 bits or 1 octet as the network portion and 3 octets for the host portion
Class A network address
Network portion = 10
Host portion =
Class B has 16 bits or 2 octets as the network portion and 2 octets for the host portion
Class B network address
Network portion =
Host portion =
Class C has 24 bits or 3 octets as the network portion and 1 octet for the host portion
Class C network address
Network portion =
Host portion = .5

5. Address Classes and Default Subnet Masks

6. Classless Inter-Domain Routing (CIDR)
Conventional network class distinctions do not exist
In classful routing a Class C can be divided into 6 subnets with 30 available hosts
This is achieved by moving the subnet boundary to the right
In CIDR the boundary can also be moved to the left
Also called supernetting

7. Calculating and Subnetting IPv4 Subnets
Class A Address
………IP address
………….Subnet Mask
The parts of the IP address that are above a zero of the mask we don’t have to worry about when we want to find the subnet address.
So the only part we have left to work out is the 168 part over the 240 part of the mask.
The magic number is 256 so = 16
So we now know that these subnets are in blocks of 16
Now we can find out the start of this subnet
Take the 168 part of the IP address and divide it by the answer 16 we got above.
168 divided by 16 = 10.5
Take the whole number of the above = 10
Multiply that 10 by 16 (10 x 16 = 160)
We now know that this subnet starts at 160 =
Our original IP Address:
The subnet the above IP address lies in
First IP address
Last IP address
Broadcast address
= Next subnet

8. Which subnet does host 172.168.74.232/20 belong to ?
If part of the IP address is above a zero on the mask then we don’t need to do anything it
The magic number is 256 so = 16
So we now know that these subnets are in blocks of 16
Take the 74 part of the IP address and divide it by the answer 16 we got above.
Take the 74 and divide it by 16 = 4.625
Take the whole number of the above = 4
Multiply that 4 by 16 = 64
We now know that this subnet starts at 64 =
The range of this is
Subnet the above IP address lies in
First IP address
Last IP address = 1 less than the broadcast
Broadcast address = 1 less than the next subnet
= Next subnet
Class B Address

9. What subnet does host 192.168.74.232/28 belong to ?
Put the IP address above the mask
The magic number is 256 so
256 – 240 (Last part of the mask) = 16
This means that in every subnet we have 16 IP addresses.
Now to find out the subnet the 232 part of the IP address is in, divide this 232 by our last answer of 16, so:
232 divided by 16 = 14.5
Now take the whole number of our last answer = 14
and multiply this by 16 to give you the start of the subnet.
14 x 16 = 224
So the answer to the question “which subnet does host /28 belong to. =
Class C Address

10. Gateways
The first interface that interprets all outbound and inbound traffic for network or subnetwork
Every node has a default-gateway, but only one default-gateway
Either configured manually or automatically (DHCP)

11. Address Translation
Public network – any user can access with little or no restrictions
Private network – restricted to clients or nodes with proper authorization
Clients behind a gateway can us any IP address scheme – legitimate or not
Clients that connect to the Internet must have a legitimate IP address
Network Address Translation (NAT)
When the user’s data reaches the gateway, the gateway replace the private IP address with a legitimate address
Overcomes low quantity of IPv4 addresses

12. Three Types of NAT Static Network Address Translation (SNAT)
Dynamic Network Address Translation (DNAT)
Port Address Translation (PAT) (Use graphic)

13. TCP/IP Mail Services
Simple Mail Transfer Protocol (SMTP) – Responsible for moving messages from one server to another
Multipurpose Internet Mail Extensions (MIME) – A standard for encoding and interpreting binary files, images, video, and non-ASCII character sets within an message
Post Office Protocol/version 3 (POP/POP3) - Application Layer protocol that is used to retrieve messages from a mail server – POP3 uses TCP and uses port 110
Internet Message Access Protocol/version 4 (IMAP/IMAP4) – Mail retrieval protocol that was supposed to replace POP3

14. Additional TCP/IP Utilities – Windows, UNIX, Linux OS’s
ipconfig – TCP/IP administration utility for use with Windows NT, 2000, XP, Vista, Sever 2003, and Server 2008 Oss.
ifconfig – TCP/IP administration utility for use with UNIX and Linux OSs
netstat – Utility that displays TCP/IP statistics, and details about TCP/IP components and connections
nbstat – Utility that provides information about NetBIOS statistics and resolve names to their IP addresses
hostname – Command that allows a client to see the hostname assigned
host – Utility used to find the IP address of a known hostname

15. Additional TCP/IP Utilities – Windows, UNIX, Linux OS’s
nslookup – Allows the user to query the DNS database from any node on the network
dig – domain information groper – Similar to nslookup. Allows the user to query DNS servere for DNS information
whois – Allows you to query the DNS registration database and get information about a domain
tracert – uses ICMP ECHO request to trace the path form one node to another
mtr – Used by UNIX or Linux OSs is a route discovery utility
route – Used on UNIX and Linux systems to view a host’s routing table

16. End of Presentation
For more information on this lesson, See Chapter 10 in the text book or the Professor
**All Slides and graphics were produced by Professor Patrick Hughes**