Network Fundamentals Practice Questions

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

1. What is a router's core forwarding decision for an IPv4 packet?

   • Select the longest matching destination IP route
   • Choose the source MAC address
   • Assign a TCP port
   • Resolve the destination hostname through DNS before forwarding

2. At which OSI layer do IPv4 and IPv6 operate?

   • Network
   • Data Link
   • Transport (Layer 4)
   • Session (Layer 5)

3. Which TCP/IP model layer most closely combines the OSI physical and data-link layers?

   • Network access (physical signaling and local frame delivery)
   • Internet (physical signaling and network routing functions)
   • Transport
   • Application

4. A host sends traffic to a destination outside its local subnet. To whose MAC address does it normally build the first Ethernet frame?

   • Its default gateway
   • The final remote host
   • The DNS server
   • The source host

5. What does ARP resolve on an IPv4 Ethernet LAN?

   • A local IPv4 address to its corresponding Ethernet MAC
   • A hostname to an IPv4 address
   • A VLAN identifier to its configured IPv4 subnet mask
   • A TCP port to an application

6. Which address is rewritten at every routed Ethernet hop while the end-to-end IPv4 source and destination usually remain unchanged?

   • Source and destination MACs
   • The IPv4 destination address in the packet header
   • The TCP destination port
   • The application payload

7. What is the purpose of the TTL field in an IPv4 header?

   • Limit lifetime to prevent persistent loops
   • Encrypt the packet
   • Identify the TCP application using its destination port
   • Select a VLAN

8. Which IPv4 header field lets a receiver reassemble fragments from the same original packet?

   • Identification
   • DSCP classification
   • Header checksum
   • Protocol identifier

9. What does the protocol field in an IPv4 header identify?

   • The encapsulated next-layer protocol
   • The negotiated speed of the outgoing switch port
   • The destination VLAN associated with the receiving port
   • The default gateway address used to forward the packet

10. Why is full-duplex Ethernet preferable to half-duplex Ethernet on a point-to-point switch link?

    • Collision-free simultaneous transmit and receive
    • It doubles the usable IPv4 address space for each endpoint
    • It removes MAC addressing by using IP addresses for local delivery
    • It eliminates STP requirements on redundant switch links

11. What does a switch do when it receives a unicast frame for a destination MAC address that is absent from its MAC table?

    • Floods it through eligible ports within the same VLAN
    • Drops it immediately
    • Routes the frame to the configured default gateway
    • Changes the frame's destination MAC

12. Which cable type is typically used to connect a PC or router Ethernet interface to a switch port?

    • Straight-through copper Ethernet cable
    • Rollover cable with a console pinout
    • Serial DCE cable
    • Fibre crossover cable only

13. Which command is most useful for quickly verifying interface IP addresses and line/protocol status on Cisco IOS?

    • show ip interface brief
    • show mac address-table
    • show access-lists
    • show version | include license

14. Which statement best describes encapsulation?

    • Adding protocol headers or trailers down the stack
    • Removing all protocol headers before a switch forwards a frame
    • A router converts every packet into a TCP segment
    • DNS replaces IP addressing

15. A switch receives a frame on Gi0/1 with source MAC A and destination MAC B. Neither address is in its MAC table. Which entry does it learn?

    • MAC B on every flooded port
    • MAC A on Gi0/1, ingress VLAN
    • Both MAC addresses on Gi0/1
    • MAC B on Gi0/1 only

16. A frame enters Gi0/1, and its destination MAC is already learned on Gi0/1 in the same VLAN. How does normal Layer 2 forwarding handle it?

    • Floods it to all other VLAN ports
    • Sends it to the default gateway
    • Filters the frame at the ingress port
    • Moves the destination entry to Gi0/2

17. A dynamically learned MAC entry expires after inactivity. What happens to the next frame for that destination if no new entry has been learned?

    • It is flooded in the VLAN except on the ingress port
    • It is permanently discarded until the switch reloads
    • It is broadcast into every VLAN
    • It is converted into an ARP request by the switch

18. An Ethernet ARP request uses destination FF:FF:FF:FF:FF:FF in VLAN 20. Which ports can normally receive the flooded request?

    • Only the port connected to the default gateway
    • All ports in all VLANs
    • Only ports with a matching destination MAC entry
    • Other eligible forwarding ports carrying VLAN 20

19. A host moves from Gi0/2 to Gi0/8 in the same VLAN and sends a frame with its original source MAC. What does normal dynamic MAC learning do?

    • Retains Gi0/2 until the switch reloads
    • Updates the source MAC entry to Gi0/8
    • Assigns the host a new MAC address
    • Removes the VLAN from both ports

20. A switch has learned host B on Gi0/3 in VLAN 10. A frame enters Gi0/1 in VLAN 10 addressed to B. With both ports forwarding, where does the switch send this known unicast?

    • Every port in VLAN 10
    • Every port except Gi0/1 regardless of VLAN
    • Gi0/3 only
    • The management interface only