Network+ Section 1

Network+ Section 1

1. OSI Layers

   • Layer 1: Cables and connections
   • Layer 2: Data links & communication through MAC addresses
     • Finds MAC address of the recipient
   • Layer 3: Network, fragments & frames
     • Provides IP address
   • Layer 4: Firewalls TCP & UDP Protocols
     • Provides TCP packet
   • Layer 5: Control Protocols (communication between apps)
   • Layer 6:Encryption & Decryption
     • Data Transfer Process
   • Layer 7: Application (The layer we see)
   • Protocol Data Units (PDU) - unit of info sent at a OSI layer
     • Maximum Transmit Unit - determine size of the IP fragments

2. Devices

   • Physical Setup: Computer - Wireless Access, Hub & Switch - Router
   • Hub
     • Half Duplex - only sends and receives data one at a time
     • Sends data to every device on the network
     • CSMA/CD Networks (Half Duplex)
       • Carrier Sense (CS): finds an available signal
       • Multiple Access (MA): allows multiple devices to access the network
       • Collision Detection (CD): detects data collision
   • Switch
     • Full Duplex - send or receive data at the same time
       • Broadcast Frames - sends data to all devices on full duplex network
     • CSMA/CA Networks (Full Duplex)
       • Collision Avoidance (CA): uses RTS & CTS with WAP to make sure data flows smoothly
         • Ready to send (RTS)
         • Clear to send (CTS)
     • Spanning Tree Protocol (STP) makes sure there are no loops/collision of data
       • Keeps track of all devices & location through MAC address
       • Configures ports for specific purposes
         • Blocking - not forwarding to prevent loops
         • Listening - not forwarding & cleaning the MAC table
         • Learning - adding devices to the MAC table
         • Forwarding - data transfer
         • Assigns numbers to configure VLAN's
       • Rapid Spanning Tree Protocol - STN update, recover yspeed increased to 6 seconds
     • Address Resolution Protocol (ARP) - finds the MAC address of other devices on the network
     • Endspan - switches with a built in power supply
   • Router
   • Wireless Access Point (WAP)
     • Forwards data based off MAC address
   • Modem
     • Backup & Utility

3. Unicast - sends data from one device to another

4. Network Segmentation

   • Virtual LAN (VLAN) - seperate switches without more hardware
     • VLAN Field - identify the sender and recipient for data transfers
     • VLAN Header - specifies the destination
     • VLAN ID's - 12 bits long, provide 4,904 possible VLAN's for one trunk
       • Normal Range: 1 - 1005
       • Extended Range: 1006 - 4094
       • Reserved: 0 & 4095
   • Trunks (IEEE 802.1Q) - connect hundreds of VLAN's
     • Trunk Interface - specify what VLAN's can communicate on the turnk

5. Demilitarized Zone (DMZ) - allows people access from outside the network

6. Midspan - line in power injector for devices that can't use POE

7. Port Mirror - examines copies of traffic

8. Static Routing - controls the route for data transfer

9. Dynamic Routing - routing tables update on their own

   • IPV4
     • OSFPv2 - open shortest path first
     • RIPv2 - routing information protocol version 2
     • EIGRP - enhanced interiror gateway rotuing protocol
     • IPv4 Configurations
       • Loopback Address - IP address that all devices are internal to those devices and all of them are using the same loopback address
         • Range: 127.0.0.1 - 127.255.255.254
         • Reserved Addresses - block addresses that will never be used on OSI Layer 3.
     • IPV4 Subnet Masks
       • Classless Inner Domain Routing (CIDR) - subnet mask is written with /24 or any number to represent the amount of 1's in the 8-bit octets
     • IP Reservations - associated MAC addresses of a server with an IP address. Prevents DHCP from reassigning IP addresses
   • Dynamic Routing Protocols
     • Distance Vector Routing Protocol - formula based on distance that determines the best re-route to fix a network problem
     • Link State Routing Protocols - formula based on the quality of speed of the connection between routers

10. Default Routing - similar to static. Syncs with both routing options. Used when no other routes match

11. Interior Gateway Protocol - routes networks on internal autonomous system.

    • Autonomous System (AS) - connected group of IP prefixes run by one or more network operators with one routing policuty

12. Exteriror GAteway Protocol - route networks on external autonomous system

    • Border Gateway Protocol (BGP) - used to connect to the internet

13. IPV6

    • Multicast - designed for IPV6. Send data to multiple devices
      • Process: DHCPv6 Multicast sends messages to multicast addresses in UDP looking for DHCP servers. Multicast responds with a list of IP addresses. DHCP client receives list of available IP addresses, picks one and sends it off.
    • Binary code much larger than IPV4. Doesn't follow 8-bit octet. More than 4 groups
      • 128-bit max
    • Internet Assign Numbers Authority (IANA) - address distribution. Provides large ranges of IP addresses to the Regional Internet Registries (RIR). Assigns smalle roups of IPV6 addresses to ISP's. ISP's give end users IPV6 address with /48 CIDR subnet
    • Dual Stack Configurations - allow for IPV4 and IPV6 on the same network.
    • 6 to 4 Addressing - similar to dual stack but this only allows IPV6 users to access data on IPV4 networks
      • IP Protocol 41 - embeds IPV6 into IPV4
    • Relay Routers - network typology, specifically where the destination and source are connected by codes
    • 4 in 6 Tunneling - Inserts IPV4 into IPV6 to reinforce connections to IPV4 networks
    • Toredo Tunneling - inserts IPV6 into IPV4
    • Neighbor Discovery Protocol (NDP) - finds other devices on IPV6 networks
      • Duplicate Address Detection (DAD) - makes sure there are no duplicate addresses
      • Router Solicitation & Advertisement - finds routers that might be on the network
    • Stateless Address Autoconfiguration (SLAAC) - devices automatically configure with IP addresses without DHCP
    • Neighbor Solicitation & Advertisement - finds the MAC address of other devices on IPV6.
    • Static Address
      • Modiefies MAC addess, creates static IPv6 address. Also known as Exteneded Unique Identifier (EUI)
        • only 48-bits. Split into two 24-bit pieces
        • FFFE? Missing 16-bits is insrterd to the middle
    • Need better notes on how to build IPv6 Addresses

14. Variable Length Subnet Mask (VLSM) - design the network in the way you need it to work.

    • Reserves two middle octets for new subnets

15. Prioritizing Traffic

    • Packer/Traffic - allows prioritization of one connection over another
    • Class of Service (CoS) - configures OSI Layer 2. Part of communication between switches
    • Differentiated Service (DiffServ) - form of QoS), implemented at OSI Layer 3. Modifies QoS bits in IPv4 header

16. Network Address Translation (NAT) - allows devices with private IP addresses to communicate with the internet by temporarily assigning a public IP address during communication

17. Access Control List (ACL) - allows or blocks traffic on the network

    • Works with NAT to determine what IP addresses need to be translated
    • Works with QoS to determine which devices get priority.

18. Circuit & Packet Sharing

    • Circuit Switching - established connection between two points before data is transferred between them
      • T1 & T3 are other forms of circuit switching
    • Packet Switching - group data into packets and sends it across the network

19. Network Typologies

    • Physical Network Map - map of all cable connections
    • Logical Network Map - map of all virtual devices and connections
    • Star Network Typology - centralized device, sits in the middle of all devices connected to it
    • Ring Network - all devices are connected in a ring form. Mainly for metro and wide area networks
    • Mesh Network - fully & partially connected areas. All connections are different
    • Bus Network - all devices are connected via single coax cable
    • Infrastructure Network - virtual connection. Used to join with wireless access points
    • AD Hoc - no pre-existing infrastructure, all devices can still communicate wirelessly

20. Wireless Network Technologies

    • Multiple-Input & Multiple-Output (MIMO) - sends multiple streams of data over the same frequency. *To one recipient*
    • Multi-User Mult-Input & Multi-Output (MU-MIMO) - sends data to multiple users over the same frequency
    • Wireless Survey Tools - provide signal coverage, potential interference, built-in tools & thrid-party tools that were installed automatically.

21. Cellular Network Standards

    • Global System for Mobile Communication (GSM) - original mobile network standard
    • Time Division Multiple Access (TDMA) - combines multiple streams into one
    • Code Division Multiple Access (CDMA) 0 uses different form of multiplex, everyone uses a different code even though they're on the same stream

22. Cloud Services & Delivery Model

    • Software As A Service - software provided by third-party.
    • Infrastructure As A Service - provided with hardware
    • Platform As A Service - no servers, software or maintenance team
    • Cloud Access Security Broker - cloud based security solutions
      • Visibility - determines what apps are in use & authorization
      • Compliance - make sure end users follow specific rules

23. DNS

    • Internal DNS - for internal servers that need to remain private
    • External DNS - managed by third party
    • Record Types
      • Resource Records (RIR) - database records of domain name services
      • Address Records - defines the IP address of the host for the IPv4 networks
      • Quad Address Records - defines the IP address of the host on the IPv6 networks
      • Service Records - find services for the network
      • Mail Exchange Servers - allows third parties to find local mail servers
      • Name Server Records - configuration details for additional name servers
      • Pointer Record - provide name server with IP address to find the DNS name
      • Text Record - contains info for other third-party services that access the DNS
        • Sender Policy Framework - prevent email spoofing
        • Domain Keys Identified Mail - digitally sign outgoing mail

24. Configuring DHCP

    • Scope Properties - list of IP addresses that are available for devices on IP subnet
    • Dynamic Allocation - big poll of addresses to give out
      • Addresses are reclaimed after period of lease
    • Automatic Allocation - device will always have IP address that is given
      • If you leave the network and come back you get the same IP address
    • Static Allocation - always have the exact same IP address with administrative privleges
    • DHCP Renewal
      • T1 Timer - checks in with the lending DHCP to renew the IP address
      • T2 Timer - if the original DHCP server is no longer available it will rebind with any DHCP server

25. Network Time Protocol (NTP)

    • Network Time Protocol - configures all devices on the network so they all have the same time & date
    • NTP Server - in charge of the clocks that needs to be updated
    • NTP Client - requests time from NTP sevrer
    • NTP Stratum Layers - measures distance from original reference clock