Two or more computers connected together DNS (Domain Name System)

Types of netwok

• LAN
• WAN

Topologies

• Ring
• Point-to-point
• Mesh
• Star
• BUS
• Tree
• HYbrid

Building blocks

• Devices (MAC Address)
• Connections - type of connection Ex.: wireless
• Switches - connect various devices
• Routers
• Network servers

OSI Model

Network Services

DNS, email, internet chat, printer sharing…

IP Addresses

• IPv4
• IPv6
• NAT public and private
  • network address translation
  • private LAN
  • public WAN

IPv4

192.168.2.14:80

• 192.168.2 = network id
• .14 = host id
• 80 = port

IPv6

Written in hexadecimal

2001:0db8:3a4d:0016:0000:0000:1c2f:1a3b

• 2001:0db8:3a4d = site prefix
• 0016 = subnet id
• 0000:0000:1c2f:1a3b = interface id

Subnet

octet octet octet octet

• class A = 16 million hosts
• class B = 65535 hosts
• class C = 254 hosts

DNS

• Domain name
• DNS Records
• Recursive Name Server
• Root Name Server
• TLD Name Server
• Authoritative Name Server

How a DNS query work

example.com

1. ask recursive name server
2. recursive server ask root name server
3. i dont know but can find in TLD name server for .com
4. i dont know but you can find in authoritative name server for example.com
5. ask authoritative name server for example.com and it returns the ip
6. recursive name server pass the ip to the client and remember the ip for sometime
7. the client receive the ip and remember for some time

Routing

Routing is moving data from one network to another

• routing tables
• routing protocols
• static routes
• dynamic routes

Network port

Associated with an ip address, there are 65535 ports

Finding your network information

• IP address information: ip address show, legacy: ifconfig
• Routes: route and netstat
• dns: nmcli, view /etc/resolv.conf

Finding remote network

• remote ip address information: dig
• routing: traceroute