CIS 527

Lecture 10 - Networking Overview

7 Layer OSI Network Model

• Application
• Presentation
• Session
• Transport - TCP/UDP
• Network - IPv4/IPv6
• Data Link - Ethernet
• Physical - 100BASE-T

Physical - 100BASE-T

Image Source: Wikipedia

Data Link - Ethernet

Image Source: Wikipedia

Routing

• Determines best way to get from point to point on a network
• Prevents loops
• Allows for redundant links in case of an error
• Simple networks use Spanning Tree Algorithm

Virtual LAN

• Partition a single layer-2 network
• Each partition is isolated
• Helps simplify network design
• Group items by function, not location

Spanning Tree Algorithm

Image Credit: Wikipedia

Spanning Tree Algorithm

Image Credit: Wikipedia

Spanning Tree Algorithm

Image Credit: Wikipedia

Spanning Tree Algorithm

Image Credit: Wikipedia

Spanning Tree Algorithm

Image Credit: Wikipedia

Spanning Tree Algorithm

Image Credit: Wikipedia

Network - IPv4

IPv4 vs. IPv6

IPv4: 32 bit Addresses
2³² = 4,294,967,296

IPv6: 128 bit Addresses
2¹²⁸ = 340,282,366,920,938,463,463,
374,607,431,768,211,456
or 340 Undecillion addresses

Network - IPv6

Image Source: Wikipedia

Network Interfaces

• Localhost
• Ethernet Adapter
• Wireless Adapter

Localhost

• a.k.a Loopback Adapter (lo)
• IP Address: 127.0.0.1
• DNS Name: localhost
• Defined in Software
• Allows a system to access itself via nework protocols

Network Adapters

• Physical hardware connections to a network
• Includes Wired (Ethernet) and Wireless adapters
• Each adapter may have 1 or more IP addresses

Windows Network Adapters
Device Manager

Windows Network Adapters
Network Connections

Ubuntu Network Adapters
/etc/hosts

/etc/network/interfaces

Ubuntu Network Adapters

IP Addresses

• Unique Identifier on a Network
• Used for packet routing
• 3 common configurations
  • Automatic - DHCP
  • Manual - Static IP Addresses
  • Automatic Private IP Addressing (APIPA)

IP Address Components

• IP Address - The identifier of this computer
• Subnet Mask - The subnet this computer belongs to
• Default Gateway - The IP address of the "way out"

Subnet

• Logical subdivision of an IP network
• Aids in routing and management
• Traffic between subnets is exchanged across routers

Classless Inter-Domain Routing

• Early internet routing assigned 4 classes of networks
  • A - 2²⁴ (16M) addresses
  • B - 2¹⁶ (65K) addresses
  • C - 2⁸ (256) addresses
  • D - multicast addresses
• Inefficient usage of IP addresses

Subnet Mask

IP Address: 192.168.5.130
11000000.10101000.00000101.10000010

Subnet Mask

IP Address: 192.168.5.130
11000000.10101000.00000101.10000010

Subnet Mask: 255.255.255.0
11111111.11111111.11111111.00000000

Subnet Mask

IP Address: 192.168.5.130
11000000.10101000.00000101.10000010

Subnet Mask: 255.255.255.0
11111111.11111111.11111111.00000000

Network Prefix: 192.168.5.0
11000000.10101000.00000101.00000000

Subnet Mask

IP Address: 192.168.5.130
11000000.10101000.00000101.10000010

Subnet Mask: 255.255.255.0
11111111.11111111.11111111.00000000

Network Prefix: 192.168.5.0
11000000.10101000.00000101.00000000

Host Part: 0.0.0.130
00000000.00000000.00000000.10000010

CIDR Notation

• Number of bits in network prefix
• /8 = Class A size
• /16 = Class B size
• /24 = 255.255.255.0 = 254 hosts
• /26 = 255.255.255.192 = 62 hosts
• /28 = 255.255.255.240 = 14 hosts
• 192.168.5.0/24

Reserved IP Address Sections

• 192.168.0.0/16
• 172.16.0.0/12
• 10.0.0.0/8
• 169.254.0.0/16(APIPA)

Dynamic Host Configuration Protocol (DHCP)

Image Source: Tech Juice

Ubuntu - dhclient

Manual Configuration

• Manually enter IP address information for hosts
• Normally used on servers and core network devices
• More control, but more work to make changes

Automatic Private IP Addressing (APIPA)

• When all else fails, your system will assign an address that is non-routable
• If your IP is like 169.254.x.x then something is not working correctly

Windows IP Configuration

Ubuntu IP Configuration

Windows Diagnostic Commands

• ping - contact IP addresses and DNS names
• tracert - trace route between hosts
• ipconfig - access IP configuration

ipconfig

• ipconfig /release
• ipconfig /renew
• ipconfig /all
• ipconfig /flushdns
• ipconfig /displaydns

Ubuntu Diagnostic Commands

• ping - contact IP addresses and DNS names
• traceroute - trace route between hosts
• ifconfig - access IP configuration
• mtr - combine ping and traceroute

Transport - TCP

Transport - UDP

TCP vs. UDP

Ports

• Individual connection points for each application on a computer
• 65535 possible ports (2¹⁶)
• Around 250 are "well known" ports with widely accepted uses for incoming connections
• Outgoing connections use high numbered "ephemeral" ports

Well Known Ports
/etc/services

• 21 - FTP
• 22 - SSH
• 25 - SMTP
• 80 - HTTP
• 443 - HTTPS
• 3389 - Remote Desktop

Windows - Sysinternals TCPView

Ubuntu - netstat

Assignments

• Lab Help Session Fridays 12:30 - 1:30 PM!
• Lab 3 - Networking Services - Due Monday, Mar 9th by 12:30 PM
• Set up Core Network Services & Network Monitoring
• Turn in:
  • CIS Transient Storage
  • via Storage Media in class