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1.0 Network Infrastructure and Connectivity

OSI Model & Encapsulation Practice Questions

OSI and TCP/IP layers, PDU names, and how encapsulation rewrites headers hop by hop.

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One solved question, so you can see how these are marked

A host sends data to a server. In what order does the data pass down through the OSI layers on the sending host?

Application, Presentation, Session, Transport, Network, Data Link, Physical

The OSI model orders the sender's functions from Application down to Physical. Encapsulation adds protocol control information where needed; it does not mean every OSI layer adds a distinct header. The Physical layer transmits signals representing bits, and the receiver processes the layers in reverse order.

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Find related practice in the CCNA path
All 7 OSI Model & Encapsulation questions in this set

Answers and explanations appear when you work through the set above.

  1. What is the correct PDU name for data at the Network layer?

    • Frame
    • Segment
    • Packet
    • Bit

  2. A packet crosses three routers over Ethernet links, with no NAT or tunneling. Which addresses are replaced when each router builds the outgoing Ethernet frame?

    • The source and destination IP addresses
    • The source and destination MAC addresses
    • The source and destination TCP port numbers
    • None of the addresses change at any point

  3. Which OSI layer is responsible for logical addressing and path determination between different networks?

    • Layer 2, Data Link
    • Layer 3, Network
    • Layer 4, Transport
    • Layer 5, Session

  4. The TCP/IP model collapses several OSI layers. Which OSI layers map to the TCP/IP Application layer?

    • Application and Presentation only
    • Application, Presentation, and Session
    • Session and Transport
    • Application only, the others have no equivalent

  5. For an Ethernet frame carrying an ordinary IPv4/TCP packet, which OSI layer adds the frame check sequence trailer?

    • Layer 4, Transport, adding a checksum trailer
    • Layer 3, Network, adding a TTL trailer
    • Layer 2, Data Link, adding the frame check sequence
    • Layer 1, Physical, adding a preamble trailer

  6. A switch forwards a frame based on information it reads from the frame header. At which OSI layer does a traditional LAN switch operate?

    • Layer 1
    • Layer 2
    • Layer 3
    • Layer 4

  7. Which statement about the relationship between a segment and a packet is correct?

    • A packet is encapsulated inside a segment by adding a TCP header
    • A segment is encapsulated inside a packet by adding an IP header
    • Segments and packets are the same PDU with two different names
    • A segment contains many packets, one per application