Networking Concepts and IPv4/IPv6 Basics

Network+ Guide to Networks Eighth Edition - Chapter 3: Addressing on Networks

• Objectives for Chapter 3
  • Find the MAC address of a computer and explain its function in network communications
  • Configure TCP/IP settings on a computer, including IP address, subnet mask, default gateway, and DNS servers
  • Explain the purpose of ports and sockets, and identify the ports of several common network protocols
  • Describe domain names and the name resolution process
  • Use command-line tools to troubleshoot problems with network addresses

Addressing Overview

• Four addressing methods
  • Data Link layer MAC address
    • 48 bits, written as six hexadecimal numbers separated by colons
    • Also known as the physical address
  • Network layer IP address
    • IPv4 addresses have 32 bits and are written as four decimal numbers (octets)
    • IPv6 addresses have 128 bits and are written as eight blocks of hexadecimal numbers
  • Transport layer port numbers
  • Application layer FQDNs, computer names, and host names
    • Fully qualified domain name (FQDN) — A unique, character-based name

MAC Addresses

• Traditional MAC addresses have two parts
  • First 24 bits are the Organizationally Unique Identifier (OUI) or manufacturer ID
    • Assigned by the IEEE
  • Last 24 bits are the extension identifier or device ID
    • Manufacturers assign each Network Interface Card (NIC) a unique device ID

IP Addresses (1 of 2)

• Static IP addresses are assigned manually by the network administrator
• Dynamic IP addresses are automatically assigned by a Dynamic Host Configuration Protocol (DHCP) server
• To view TCP/IP settings on a Windows 10 computer:
  • Open Network and Sharing Center in Control Panel
  • Click Change adapter settings
• Brief explanation of settings:
  • Gateway - Device used for access to the outside world
  • Subnet mask - Used to indicate the network portion (network ID) and host portion (host ID) of an IP address
  • DNS server - Server responsible for tracking computer names and their IP addresses

IP Addresses (2 of 2)

• Using the ipconfig utility in Command Prompt to find current TCP/IP settings
• Two types of IP addresses:
  • IPv4 - A 32-bit address
  • IPv6 - A 128-bit address

IPv4 Addresses (1 of 7)

• IPv4 addresses are 32-bit addresses organized into four groups of 8 bits each (octets)
• Each octet can be any number from 0 to 255
• Some IP addresses are reserved

IPv4 Addresses (2 of 7)

• Classful addressing
  • Dividing line between network and host portions is determined by the numerical range the IP address falls in
  • Classful IPv4 addresses are divided into five classes
    • Class A, Class B, Class C, Class D, and Class E
    • Classes A, B, and C are public IP addresses available for use on the internet
• A company can use private IP addresses on its private networks
• IEEE recommended IP addresses for private networks:
  • 10.0.0.0 through 10.255.255.255 — For few networks/many hosts
  • 172.16.0.0 through 172.31.255.255 — For many networks/hosts and many few hosts

IPv4 Addresses (3 of 7)

• Table of IP address classes
• Shows the network octets, approximate number of possible networks, and approximate number of IP addresses per network

IPv4 Addresses (4 of 7)

• Class D and E addresses are not available for general use
  • Class D — Used for multicasting
  • Class E — Used for research
• Table of reserved IP addresses

IPv4 Addresses (5 of 7)

• Network Address Translation (NAT) — Technique to conserve public IP addresses
• Address translation — Gateway device substitutes private IP addresses with its own public address
• Port Address Translation (PAT) — Process of assigning a TCP port number to each ongoing session between a local host and Internet host

IPv4 Addresses (6 of 7)

• Figure of Port Address Translation (PAT) showing network communication and how devices have translated IP addresses

IPv4 Addresses (7 of 7)

• Two variations of NAT
  • SNAT (Static Network Address Translation) - Gateway assigns the same public IP address to a host each time it makes a request to access the internet
  • DNAT (Dynamic Network Address Translation) - Gateway has a pool of public addresses to assign to a local host when it makes a request to access the internet

IPv6 Addresses (1 of 7)

• An IPv6 address has 128 bits written as eight blocks of hexadecimal numbers separated by colons
• Example: 2001:0000:0B80:0000:0000:00D3:9C5A:00CC (can be shortened)

IPv6 addresses (2 of 7)

• IPv6 terminology
  • Link - Any LAN bounded by routers
  • Interface - Node's attachment to a link
  • Dual stacked - Network configured to use both IPv4 and IPv6
  • Tunneling - Method used by IPv6 to transport IPv6 packets through or over an IPv4 network
  • Interface ID - Last 64 bits or four blocks of an IPv6 address (identify the interface)
  • Neighbors - Two or more nodes on the same link

IPv6 Addresses (3 of 7)

• Types of IPv6 addresses
  • Unicast - Specifies a single node on a network
    • Global unicast - Can be routed on the internet
    • Link local unicast - Can be used for communicating with nodes on the same link
  • Multicast - Packets delivered to all nodes on a network
  • Anycast - Can identify multiple destinations, deliver packets to the closest destination

IPv6 Addresses (4 of 7)

• Figures of Broadcasting, Multicasting, Anycasting, and Unicasting

IPv6 Addresses (5 of 7)

• Table of address prefixes for different types of IPv6 addresses

Ports and Sockets (1 of 3)

• Port numbers ensure data is transmitted to the correct process among multiple processes on a computer
• Socket consists of a host's IP address and the port number of an application running on that host
• A colon separates the two values
• Port numbers are divided into three types
  • Well-known ports (0-1023)
  • Registered ports (1024-49151)
  • Dynamic and private ports(49152-65535)

Ports and Sockets (2 of 3)

• Figure of a virtual connection, showing request for Telnet connection on port 23

Ports and Sockets (3 of 3)

• Protocols not yet covered include, TFTP, NTP, LDAP, SMB, SIP, and H.323

Domain Names and DNS (1 of 3)

• Character-based names are easier to remember than numerical IP addresses
• Last part of an FQDN is called the Top-Level Domain (TLD)
• Domain names must be registered with an internet naming authority
• ICANN restricts what type of hosts can be associated with specific TLDs (e.g., .arpa, .mil, .int, .edu, .gov).
• The process of discovering an IP address when you know the FQDN is called name resolution.

Domain Names and DNS (2 of 3)

• Table of some well-known top-level domains (TLDs) and their associated organization types

Domain Names and DNS (3 of 3)

• DNS — Application-layer client-server system made up of
  • Namespace — Entire collection of computer names and their associated IP addresses
  • Name servers — Hold databases organized hierarchically
  • Resolvers — DNS client that requests information from DNS name servers

Namespace Databases

• Each organization providing host services is responsible for providing and maintaining its own DNS authoritative servers for public access
• Authoritative server — Authority on computer names and their IP addresses
• Domains an organization manages are called a DNS zone

Name Servers (1 of 4)

• Four common types of DNS servers
  • Primary DNS server — Authoritative name server for the organization (holds authoritative DNS database for the organization's zones)
  • Secondary DNS server — Backup authoritative name server
  • Caching DNS server — Accesses public DNS data and caches DNS info it collects
  • Forwarding DNS server — Receives queries from local clients (doesn't resolve the queries)

Name Servers (2 of 4)

• DNS name servers are organized in a hierarchical structure
• At the root level, 13 clusters of root servers hold information to locate top-level domain (TLD) servers
• TLD servers hold info about authoritative servers owned by various organizations

Name Servers (3 of 4)

• Figure illustrating queries for name resolution (e.g., www.mdc.edu)

Name Servers (4 of 4)

• Ways the resolution process can become complex
  • Caching server isn't always the same machine as the authoritative server
  • Name servers within a company might not have access to root servers
  • A TLD name server might be aware of an intermediate name server rather than the authoritative name server
• Two types of DNS requests
  • Recursive — Demands resolution or the answer "It can't be found"
  • Iterative — Local server issues queries to other servers (only provides info if it has it)

Resource Records in a DNS Database

• Several resource records kept in a DNS database
  • A (Address) record - Stores name-to-address mapping for a host
  • AAAA record - Holds name-to-address mapping, IPv6 address
  • CNAME record - Holds alternative names for a host
  • PTR record - Used for reverse lookups
  • NS record - Indicates authoritative name server for a domain
  • MX record - Identifies mail server, used for email traffic
  • SRV record - Identifies hostname and port of a computer hosting a network service
  • TXT record - Holds any type of free-form text

DNS Server Software (1 of 2)

• BIND (Berkeley Internet Name Domain)-Most popular DNS server software (open source)
• Microsoft DNS Server-Built-in DNS service in the Windows Server OS
• For more secure networks:
  • Internal and external DNS queries should be handled by different DNS servers
  • Use a firewall to filter or block traffic between networks
  • DMZ (demilitarized zone) — Area between firewalls

DNS Server Software (2 of 2)

• Figure showing DNS services handled by two different servers, protecting the internal network

Troubleshooting Address Problems

• Event Viewer is often the first place to troubleshoot problems
• Example: Event Viewer showing issues with a printer driver

Troubleshooting Tools (1 of 12, 2 of 12, ... 12 of 12)

• Using command-line tools for troubleshooting network issues
• Examples of helpful command-line tools: ping, ipconfig, ifconfig (Linux), nslookup, and dig (Linux)

Common Network Issues (1 of 3, 2 of 3, 3 of 3)

• Incorrect time
• DHCP issues: Checking DHCP server settings and DHCP scope for client support, considering lease time
• Network connection configuration issues