IT 520 Module 3 and 4

Layer 2 Addressing

Uses MAC addresses (physical hardware addresses) for communication within the same network segment.

Layer 3 Addressing

Uses IP addresses (logical addresses) for routing data between different networks.

Layer 4 Addressing

Uses port numbers to identify specific applications or services on a host.

Class A

1.0.0.0 – 126.255.255.255
Default Subnet Mask: 255.0.0.0
Large networks (16 million hosts per network).

Class B

128.0.0.0 – 191.255.255.255
Default Subnet Mask: 255.255.0.0
Medium-sized networks (65,000 hosts per network).

Class C

192.0.0.0 – 223.255.255.255
Default Subnet Mask: 255.255.255.0
Small networks (254 hosts per network).

Class D

224.0.0.0 – 239.255.255.255
Used for multicast.

Class E

240.0.0.0 – 255.255.255.255
Experimental; not used for regular networking.

Public IP Addresses

Globally unique and routable on the internet.

Private IP Addresses

Used within private networks; not routable on the internet.
Ranges:

• Class A: 10.0.0.0 – 10.255.255.255

• Class B: 172.16.0.0 – 172.31.255.255

• Class C: 192.168.0.0 – 192.168.255.255

Required Addressing on a Host

IP Address, Subnet Mask, Default Gateway, DNS Server

IP Address

Identifies the device on the network.

Subnet Mask

Defines the network and host portions.

Default Gateway

The route out of the local network.

DNS Server

Resolves domain names to IP addresses.

IPv6 Address

128-bit address written in hexadecimal.

Purpose of IPv7

Provides a vastly larger address space and eliminates the need for NAT.

Data Encapsulation

The process of wrapping data with protocol information at each layer of the OSI model.

Encapsulation Order

Application → Transport → Network → Data Link → Physical

De-Encapsulation Order (receiving data)

Physical → Data Link → Network → Transport → Application

Application Layer

Data

Transport Layer

Segments (uses port numbers)

Network Layer

Packets (uses IP addresses)

Data Link Layer

Frames (uses MAC addresses)

Physical Layer

Bits (raw data transmission)

TCP (transmission Control Protocol)

• Connection-oriented

• Reliable, ordered, and error-checked

  • Used for web (HTTP/HTTPS), email (SMTP), file transfer (FTP)

UDP (User Datagram Protocol)

• Connectionless

• Fast but unreliable

• Used for streaming, gaming, and VoIP

Common TCP Ports

HTTP – 80
HTTPS – 443
FTP – 20/21
SMTP – 25
SSH – 22
Telnet – 23

Common UDP Ports

DNS – 53
DHCP – 67/68
TFTP – 69
SNMP – 161/162

ARP (Address Resolution Protocol) purpose

Resolves IP addresses (Layer 3) to MAC addresses (Layer 2) on a local network.

ARP Taple

Stored locally; lists known IP-to-MAC mappings.

ARP Request

Broadcast asking, “Who has this IP?”

ARP Reply

Response from the device owning that IP address with its MAC address.

Telenet

• Remote terminal protocol using plaintext.

• Insecure (data is not encrypted).

• Port 23.

SSH (Secure Shell)

• Encrypted remote access for secure logins and management.

• Port 22.

• Preferred alternative to Telnet.