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← Unit 3: Networking

TEJ3M · Unit 3 test review

Networking: Test Review

Everything for the Unit 3 test on one page: the key facts from all 4 lessons, the mistakes that cost the most marks, and a practice test that points you back to the lessons you need.

Key facts

Network Types, Topologies and Media

  • LAN: one site, you own it. WAN: spans sites over infrastructure you do not own.
  • Client-server centralizes accounts, permissions and backups; peer-to-peer has no central administration.
  • Star is the standard wired topology; a single cable break affects only one device.
  • Copper Ethernet is limited to 100 m including patch cables.
  • Twisting in UTP cancels interference — do not untwist more than about 13 mm at a connector.
  • Switch ports each get full bandwidth; wireless clients on one access point share it.

The OSI and TCP/IP Models

  • OSI layers 1–7: Physical, Data link, Network, Transport, Session, Presentation, Application.
  • Encapsulation unit names: data → segment → packet → frame → bits.
  • IP addresses stay the same end to end; MAC addresses are rewritten at every hop.
  • Switch = layer 2 (MAC). Router = layer 3 (IP).
  • TCP is connection-oriented, acknowledged, ordered and retransmitted; UDP is none of those and therefore faster.
  • An IP address identifies a machine; a port number identifies a program on it.
  • Ports to know: 22 SSH, 25 SMTP, 53 DNS, 80 HTTP, 443 HTTPS.

IP Addressing and Subnetting

  • An IPv4 address is 32 bits, written as four octets of 0–255.
  • The subnet mask is always contiguous 1s then 0s; /24 = 255.255.255.0.
  • Usable hosts = .
  • Network address: all host bits 0. Broadcast address: all host bits 1. Neither is assignable.
  • Private ranges: 10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16.
  • 169.254.x.x (APIPA) means DHCP failed.
  • DHCP sequence: Discover, Offer, Request, Acknowledge (DORA).
  • IPv6 is 128 bits, written in hex groups, with :: replacing one run of zeros.

Network Devices, Cabling and Security

  • Hub = layer 1, switch = layer 2 (MAC), router = layer 3 (IP).
  • A switch learns MAC addresses from the source address of incoming frames, and floods when it does not know a destination.
  • T568A and T568B differ only by swapping the orange and green pairs.
  • Straight-through: same standard both ends. Crossover: A on one end, B on the other.
  • Use WPA3, or WPA2 with AES. Never WEP.
  • Hidden SSIDs and MAC filtering provide no meaningful security.
  • Troubleshoot from layer 1 upward: cable, link light, IP address, gateway, internet, DNS.

Where marks get lost

  • Defining a WAN purely by size. The defining feature is that it crosses infrastructure you do not own. (Network Types, Topologies and Media)
  • Calling a home router's network a client-server network. It is peer-to-peer; the router is a gateway, not a file server. (Network Types, Topologies and Media)
  • Believing the 100 m limit applies only to the permanent run — patch cables at both ends count too. (Network Types, Topologies and Media)
  • Thinking a wireless access point gives every client its full rated speed. Clients share airtime; switch ports do not. (Network Types, Topologies and Media)
  • Confusing physical and logical topology — old Ethernet was a physical star and a logical bus at the same time. (Network Types, Topologies and Media)
  • Reversing the OSI layer order. Layer 1 is Physical at the bottom; layer 7 is Application at the top. (The OSI and TCP/IP Models)
  • Saying MAC addresses travel end to end. They are rewritten at every hop; only IP addresses persist. (The OSI and TCP/IP Models)
  • Calling every unit a "packet". Segment at layer 4, packet at layer 3, frame at layer 2. (The OSI and TCP/IP Models)
  • Assuming TCP is always the better choice. For real-time media its guarantees actively hurt. (The OSI and TCP/IP Models)
  • Mixing up port and IP. IP finds the machine; the port finds the program on it. (The OSI and TCP/IP Models)
  • Thinking a switch reads IP addresses. A plain switch works at layer 2 and only sees MAC addresses. (The OSI and TCP/IP Models)
  • Forgetting to subtract 2 when counting usable hosts. (IP Addressing and Subnetting)
  • Assigning the network address or broadcast address to a device. (IP Addressing and Subnetting)
  • Assuming two addresses on the same first three octets are on the same subnet. The mask decides, not the digits. (IP Addressing and Subnetting)
  • Reading /26 as "26 hosts". It is 26 network bits, leaving 6 host bits and 62 usable addresses. (IP Addressing and Subnetting)
  • Trying to fix a 169.254 address by changing DNS settings. It means DHCP never replied at all. (IP Addressing and Subnetting)
  • Writing a subnet mask with non-contiguous 1s, such as 255.255.0.255. Masks are always 1s then 0s. (IP Addressing and Subnetting)
  • Calling a home router just a router. It is a router, switch, access point, firewall and often a modem in one box. (Network Devices, Cabling and Security)
  • Thinking a switch reads IP addresses. A plain layer 2 switch only sees MAC addresses. (Network Devices, Cabling and Security)
  • Relying on a hidden SSID or MAC filtering for security. Both are bypassed trivially. (Network Devices, Cabling and Security)
  • Starting troubleshooting at DNS. Check the physical link and IP configuration first. (Network Devices, Cabling and Security)
  • Untwisting far too much cable when terminating, which destroys interference rejection and causes intermittent errors. (Network Devices, Cabling and Security)
  • Leaving WEP or WPA/TKIP enabled on old equipment because "it still works". WEP can be broken in minutes. (Network Devices, Cabling and Security)

Practice test

24 questions from across the unit. Each one shows the lesson it comes from.

  1. Network Types, Topologies and Media
    1
    Which best describes the difference between a LAN and a WAN?
  2. Network Types, Topologies and Media
    2
    In a star topology, what happens when one cable between a computer and the switch is cut?
  3. Network Types, Topologies and Media
    3
    Thirty laptops connect to one wireless access point rated at 600 Mb/s. What throughput can each expect?
  4. Network Types, Topologies and Media
    4
    Match each network scale to its example.
    PAN
    LAN
    MAN
    WAN
  5. Network Types, Topologies and Media
    5
    Order these network types from smallest scale to largest.
    1. 1LAN
    2. 2WAN
    3. 3MAN
    4. 4PAN
  6. Network Types, Topologies and Media
    6
    A technician terminates a Cat 6 cable but untwists 4 cm of each pair to make the wires easier to arrange. What is the likely result?
  7. The OSI and TCP/IP Models
    7
    Order the OSI layers from layer 1 to layer 4.
    1. 1Data link
    2. 2Transport
    3. 3Network
    4. 4Physical
  8. The OSI and TCP/IP Models
    8
    What is the unit of data at the network layer called?
  9. The OSI and TCP/IP Models
    9
    Which protocol would a live multiplayer game most likely use for player position updates?
  10. The OSI and TCP/IP Models
    10
    A packet travels from Toronto to Tokyo through eleven routers. What happens to its addresses?
  11. The OSI and TCP/IP Models
    11
    Why does a computer need port numbers at all, when it already has an IP address?
  12. The OSI and TCP/IP Models
    12
    TCP's three-way handshake exists to:
  13. IP Addressing and Subnetting
    13
    How many usable host addresses does a /27 subnet provide?
  14. IP Addressing and Subnetting
    14
    What is the broadcast address for the subnet 192.168.5.64/26?
  15. IP Addressing and Subnetting
    15
    Which address is NOT usable as a host address on the subnet 172.16.8.0/24?
  16. IP Addressing and Subnetting
    16
    A subnet must hold at least 500 hosts. What is the smallest number of host bits required?
    bits
  17. IP Addressing and Subnetting
    17
    Put the DHCP process in order.
    1. 1Server sends Offer
    2. 2Server sends Acknowledge
    3. 3Client sends Request
    4. 4Client broadcasts Discover
  18. IP Addressing and Subnetting
    18
    Two hosts are 10.1.1.5/24 and 10.1.2.5/24 with no router between them. Can they communicate?
  19. Network Devices, Cabling and Security
    19
    Why does a switch provide better performance than a hub?
  20. Network Devices, Cabling and Security
    20
    A cable has T568B on both ends. What kind of cable is it?
  21. Network Devices, Cabling and Security
    21
    Order these troubleshooting steps from lowest OSI layer to highest.
    1. 1Check the IP address and subnet mask with ipconfig
    2. 2Run nslookup to test DNS
    3. 3Ping the default gateway
    4. 4Check the cable is connected and the link light is on
  22. Network Devices, Cabling and Security
    22
    Match each device to the OSI layer it operates at.
    Hub
    Switch
    Router
    Application firewall
  23. Network Devices, Cabling and Security
    23
    A switch receives a frame for a MAC address it has never seen. What does it do?
  24. Network Devices, Cabling and Security
    24
    Why must you avoid untwisting more than about 13 mm of each pair when terminating UTP?

Endless drill

Fresh numbers every time, for the calculation questions in this unit.

Endless drillnew numbers every time

Generating a problem…

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