Ready to supercharge your CCNA prep? Our Ace CCNA Quiz: TCP Protocols & Broadcast Domains is a free, scored CCNA practice quiz designed to challenge both your theory and analytical skills. In this Cisco networking quiz, you'll face real-world scenarios: when you refer to the exhibit, how many broadcast domains are displayed? Plus, test your recall on which three application layer protocols use TCP - choose three to advance your expertise. Lock in your confidence with detailed explanations and immediate feedback on every answer. Whether you're gearing up for the CCNA exam or love network puzzles, dive in now, explore our TCP & UDP protocols deep dive and tackle a full CCNA practice test to see how you rank!
Which layer of the OSI model does TCP operate on?
Transport
Application
Network
Data Link
TCP is defined at the Transport layer (Layer 4) of the OSI model, responsible for end-to-end communication and reliability. It provides connection-oriented services using sequence numbers and acknowledgments. For more details, see Cisco OSI Model Overview.
Which protocol uses port 80 by default?
HTTP
SMTP
FTP
DNS
HTTP uses TCP port 80 by default to serve web traffic. This port is standardized for web browsers to request and retrieve web pages. For more information, see IANA service names and port numbers.
Which of these is a connectionless protocol?
UDP
TCP
HTTP
ARP
UDP (User Datagram Protocol) is a connectionless protocol at the Transport layer that sends datagrams without establishing a session. It offers low overhead and no guarantee of delivery. See Cisco UDP Configuration Guide.
What device separates broadcast domains?
Router
Switch
Hub
Bridge
Routers block broadcast traffic, thus creating separate broadcast domains on each of their interfaces. Switches and bridges forward broadcasts by default, while hubs simply repeat all signals. More at Cisco on Broadcast Domains.
Which protocol is used to resolve IP addresses to MAC addresses?
ARP
RARP
DNS
ICMP
Address Resolution Protocol (ARP) translates IPv4 addresses to MAC addresses on a LAN. It broadcasts a request packet and receives the mapping in a reply. Read more at Cisco ARP Overview.
Which layer of the OSI model uses logical addressing with IP?
Network
Transport
Data Link
Physical
The Network layer (Layer 3) uses logical addressing like IPv4 or IPv6 to route packets across networks. It determines the best path and handles forwarding between routers. See Cisco IP Routing Principles.
Which default port does FTP use for data transfer?
20
21
22
23
FTP uses TCP port 20 for data channel and port 21 for control channel by default. The data port is used for actual file transfers after the control session is established. Refer to RFC 959.
Which field in a TCP segment ensures data is delivered in order?
Sequence Number
Checksum
Acknowledgment Number
Window Size
The Sequence Number field identifies the order of bytes in the byte stream, allowing the receiver to reorder segments if they arrive out of sequence. Acknowledgments confirm receipt. For more, see Cisco TCP Overview.
What is the broadcast MAC address?
FF:FF:FF:FF:FF:FF
00:00:00:00:00:00
FF:00:FF:00:FF:00
AA:BB:CC:DD:EE:FF
The broadcast MAC address of all ones (FF:FF:FF:FF:FF:FF) is used to deliver a frame to every node on the local network. Switches forward broadcasts out all active ports in the VLAN. See Cisco Broadcast Forwarding.
Which Cisco IOS command shows VLAN information?
show vlan brief
show ip route
show interfaces status
show mac address-table
The 'show vlan brief' command displays VLAN IDs, names, status, and associated ports on a Cisco switch. It's the quick way to verify VLAN configuration. Details at Cisco VLAN Configuration.
What is the broadcast address for the subnet 192.168.1.0/24?
192.168.1.255
192.168.1.0
192.168.1.1
192.168.1.254
In a /24 network, the broadcast address is the highest address in the range, ending in .255. Hosts send to this address to reach all devices on the subnet. For reference, see Cisco IP Broadcast.
Which of the following is a valid unicast IPv4 address?
192.168.0.1
224.0.0.1
255.255.255.255
0.0.0.0
192.168.0.1 is in the private unicast range. 224.0.0.1 is multicast, 255.255.255.255 is limited broadcast, and 0.0.0.0 is a default route. See IANA IPv4 Address Space.
Which protocol is commonly used for email retrieval?
POP3
SMTP
IMAP
HTTP
POP3 (Post Office Protocol v3) is used by clients to retrieve email from a mail server. It downloads and optionally deletes messages. SMTP is for sending mail. More details at RFC 1939.
Which TCP mechanism implements flow control?
Sliding window
Checksum
Three-way handshake
Congestion avoidance
TCP uses a sliding window for flow control, allowing the receiver to inform the sender how much data it can accept. This prevents buffer overflow. More at Cisco TCP Flow Control.
Which port number is assigned to DNS by default?
53
23
161
69
DNS queries and responses use UDP or TCP port 53 by default. UDP is common for queries, TCP is used for zone transfers or larger responses. See IANA DNS Port Assignment.
Which OSI layer is responsible for end-to-end communication and reliability?
Transport
Network
Session
Data Link
The Transport layer (Layer 4) provides end-to-end communication services, reliability, segmentation, and flow control. TCP and UDP are key protocols here. For more, see Cisco Transport Layer.
Which TCP flag indicates the termination of a connection?
FIN
SYN
RST
PSH
The FIN flag signals that the sender has finished sending data and wants to close the connection. The other side responds with its own FIN/ACK to terminate. See Cisco TCP Flags.
Which TCP congestion control algorithm starts by increasing the congestion window exponentially?
Slow start
Fast recovery
Congestion avoidance
Retransmission timeout
Slow start doubles the congestion window each RTT until a threshold is reached, then switches to congestion avoidance. This quickly probes available bandwidth. See RFC 5681.
Which Cisco command displays the ARP cache?
show arp
show ip route
show mac address-table
show interfaces
The 'show arp' command lists IP-to-MAC mappings in the ARP table. This is useful for troubleshooting layer 2 resolution. Details at Cisco ARP.
Which statement is FALSE about broadcast domains?
Routers forward broadcasts
Switches forward broadcasts within a VLAN
Bridges forward broadcasts
Each router interface is a new broadcast domain
Routers do not forward broadcasts—they separate broadcast domains. Switches and bridges forward broadcast frames within the same VLAN or segment. See Cisco Broadcast Domains.
How many bits are in an IPv4 address?
32
64
128
48
IPv4 uses 32-bit addresses, typically written in dotted decimal format across four octets. This allows for about 4.3 billion unique addresses. See RFC 791.
Which utility uses ICMP Echo messages?
ping
traceroute
telnet
ssh
Ping sends ICMP Echo Request and listens for Echo Reply to test reachability and measure round-trip time. traceroute uses UDP or ICMP depending on the OS. See Cisco Ping/Traceroute.
Which TCP flag initiates the three-way handshake?
SYN
ACK
FIN
RST
The SYN flag is sent in the first packet from client to server to initiate a TCP connection. The server responds with SYN-ACK, then the client sends ACK. More at Cisco TCP Handshake.
What is the primary purpose of the ACK flag in TCP?
To acknowledge received data
To start a connection
To request retransmission
To close a connection
The ACK flag indicates that the Acknowledgment Number field is significant and confirms receipt of data. It ensures reliable delivery by informing the sender which bytes have been received. See Cisco TCP ACK.
Which UDP port does NTP use by default?
123
69
161
520
Network Time Protocol (NTP) uses UDP port 123 for time synchronization between clients and servers. This port is standardized across platforms. See RFC 5905.
Untagged packets on a trunk are placed into which VLAN by default?
Native VLAN 1
Management VLAN 10
Native VLAN 0
Any access VLAN
By default, VLAN 1 is the native VLAN on Cisco trunks, and untagged traffic is assigned to it. Changing the native VLAN is recommended for security. See Cisco 802.1Q Native VLAN.
Which IOS command assigns an IP address to an interface?
ip address
set ip
assign ip
interface ip
In interface configuration mode, 'ip address ' sets the IPv4 address and subnet mask. This command enables layer 3 functionality on that interface. See Cisco IP Addressing.
At which OSI layer does NAT operate?
Network
Data Link
Transport
Application
NAT modifies IP headers and operates at the Network layer to translate private addresses to public ones. It does not inspect transport or application payload. For more, see Cisco NAT Overview.
Which protocol uses TCP port 443?
HTTPS
SSH
Telnet
SMTP
HTTPS uses TCP port 443 to provide encrypted web communications using TLS/SSL. This port ensures secure transactions between clients and servers. More at IANA HTTPS Port.
Which IP header field specifies fragmentation offset?
Fragment Offset
Identification
Flags
TTL
The Fragment Offset field indicates where in the original datagram this fragment belongs, measured in 8-byte units. It’s used for reassembly. See RFC 791.
Which IOS command saves the running configuration to startup configuration?
copy running-config startup-config
write erase
reload
clear config all
'copy running-config startup-config' writes the active configuration to NVRAM so it persists after reload. It’s essential after changes. More details at Cisco copy Command.
Which Cisco protocol negotiates trunking dynamically?
DTP
VTP
STP
HSRP
DTP (Dynamic Trunking Protocol) negotiates whether a link becomes a trunk or access port. VTP manages VLANs across switches but does not negotiate trunk connections. See Cisco DTP.
Which TCP mechanism uses a congestion window (cwnd) to control data flow under congestion?
Congestion control
Flow control
Error control
Connection establishment
TCP congestion control uses the congestion window (cwnd) to limit the amount of unacknowledged data in the network under congestion conditions. Flow control uses the receiver window separately. Read more at RFC 5681.
What does the TCP window scale option modify?
Receive window size
Congestion window
Segment size
Timeout interval
The TCP window scale option extends the 16-bit window field, allowing the receive window to be scaled and supporting high-bandwidth links. See RFC 7323.
What is the default MTU size on Ethernet networks?
1500 bytes
1400 bytes
1492 bytes
1518 bytes
Standard Ethernet frames have a Maximum Transmission Unit (MTU) of 1500 bytes for payload. This excludes the Ethernet header and trailer. More at IEEE 802.3.
Which IOS command clears the ARP cache on a Cisco device?
clear arp
clear mac-address-table
clear ip route
clear interfaces
The 'clear arp' command removes all entries from the ARP cache, forcing the device to relearn IP-to-MAC mappings. It’s useful after topology changes. See Cisco clear arp.
If a switch has VLANs 10, 20, and 30, how many broadcast domains exist?
3
1
2
4
Each VLAN defines its own broadcast domain. With VLANs 10, 20, and 30, there are three separate broadcast domains. Find out more at Cisco VLANs.
Which Cisco IOS command shows trunking and VLAN information on interfaces?
show interface trunk
show vlan brief
show interfaces status
show ip interface brief
'show interface trunk' displays trunk ports and allowed VLANs. It’s essential for troubleshooting VLAN tagging issues. See Cisco trunking.
What should you check first when diagnosing broadcast storm issues?
Physical loops or cabling
DNS configuration
ARP table size
MTU size
Broadcast storms often result from physical loops. Verifying cabling and STP status is the first step. For guidance, see Cisco broadcast storm.
Which transport protocol does BGP use to exchange routing information?
TCP
UDP
ICMP
SCTP
BGP uses TCP port 179 for reliable transport of routing updates. This ensures session establishment and ordered delivery. More at RFC 4271.
Which protocol does the standard traceroute utility on Linux use by default?
UDP
ICMP
TCP
GRE
The default traceroute on many Unix/Linux systems sends UDP datagrams to high-numbered ports and relies on ICMP Time Exceeded replies to map the path. See traceroute man page.
ARP is considered a Layer 2.5 protocol because it operates between which two layers?
Data Link and Network
Transport and Application
Physical and Data Link
Network and Transport
ARP resolves IP addresses (Network layer) to MAC addresses (Data Link layer), so it logically operates between Layers 2 and 3. This is often called Layer 2.5. See Cisco ARP Overview.
What is the purpose of the IP TTL field?
Prevent routing loops
Prioritize packets
Fragment packets
Encrypt payload
The Time To Live (TTL) field decrements at each hop to prevent indefinite packet circulation due to routing loops. When TTL hits zero, the packet is dropped and an ICMP Time Exceeded message is sent. See RFC 791.
Which configuration step helps prevent VLAN hopping attacks?
Disable DTP and use nonegotiate on trunks
Enable CDP on all ports
Use VLAN 1 for all management tasks
Allow all VLANs on trunk by default
Disabling DTP (Dynamic Trunking Protocol) and setting trunk ports to 'nonegotiate' prevents unauthorized devices from negotiating trunk links and VLAN hopping. See Cisco VLAN Security.
Which tool can capture and analyze the TCP three-way handshake at packet level?
Wireshark
telnet
ping
tracert
Wireshark is a packet analyzer that can capture live traffic, display SYN, SYN-ACK, ACK flags, and analyze the TCP handshake. It helps in deep troubleshooting. More at Wireshark.
Which UDP port does TFTP use by default?
69
53
161
520
Trivial File Transfer Protocol (TFTP) uses UDP port 69 for initial requests. Subsequent data and ACKs use ephemeral ports. For details, see RFC 1350.
Which technique can mitigate SYN flood attacks in TCP?
SYN cookies
Window scaling
Delayed ACK
Slow start
SYN cookies are a defense against SYN floods by encoding state in the initial sequence number and avoiding resource allocation until the handshake completes. See RFC 4987.
If you configure 'passive-interface' for EIGRP on a router link, what happens to EIGRP updates on that interface?
No updates are sent or received on that interface
Updates are sent but not received
Updates are received but not sent
No effect on updates
The 'passive-interface' command suppresses both sending and receiving of EIGRP Hellos on that interface, preventing adjacency formation. Routes are still advertised via other interfaces. See Cisco EIGRP passive-interface.
What issue arises when two VLANs carry overlapping IP subnets across a trunk?
ARP resolution conflicts and traffic misdelivery
STP loops
DHCP starvation
Link aggregation failures
Overlapping subnets across VLANs cause ARP entries to conflict, leading to traffic being sent to incorrect MAC addresses or dropped. Proper subnet design and VLAN separation are required. More at NetworkLessons Overlapping Subnets.
Which feature allows multiple IP subnets on the same switch interface?
Secondary IP addressing
Sub-interface encapsulation
VRRP
HSRP
Secondary IP addressing lets you assign more than one IP network to a single interface, enabling multiple subnets to coexist. It’s configured with the 'secondary' keyword. See Cisco IP Secondary Address.
Which TCP feature delays sending ACKs to reduce protocol overhead?
Delayed ACK
Selective ACK
Window scaling
Nagle's algorithm
Delayed ACK holds acknowledgments briefly to piggyback them onto outgoing data or send fewer ACKs, reducing overhead. It can interact with Nagle’s algorithm. See RFC 1122.
In TFTP transfers, which port does the server use to send data after the initial request?
An ephemeral port >1023
UDP port 69
TCP port 20
TCP port 69
After the TFTP client’s initial request on UDP port 69, the server responds from a newly allocated ephemeral port >1023 for data transfer. This prevents conflicts when multiple transfers occur. See RFC 1350.
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Apply knowledge to answer the question which three application layer protocols use TCP choose three with confidence.
Analyze Broadcast Domain Scenarios -
Refer to the exhibit how many broadcast domains are displayed and determine domain boundaries in network diagrams.
Identify Knowledge Gaps -
Receive instant feedback on quiz responses to pinpoint areas needing further CCNA practice and review.
Reinforce CCNA Exam Prep -
Utilize this CCNA practice quiz to solidify understanding of networking fundamentals and boost test readiness.
Evaluate Test Performance -
Interpret scored results from this Cisco networking quiz to track progress and set goals for exam success.
Cheat Sheet
TCP-Based Application Layer Protocols -
Focus on protocols such as HTTP (port 80), FTP (ports 20/21), and SMTP (port 25) that rely on TCP for reliable delivery. Recall the mnemonic "HFS" (HTTP, FTP, SMTP) to quickly identify which three application layer protocols use TCP. These protocols ensure ordered, error-checked data streams as defined in RFC 793.
Well-Known Port Number Range -
Ports 0 - 1023 are reserved for core TCP services like HTTP (80), HTTPS (443), and FTP control (21). Recognizing these assignments helps you match application layer protocols to TCP ports on the CCNA practice test. Source: IANA Service Name and Transport Protocol Port Number Registry.
TCP Three-Way Handshake -
Understand the SYN → SYN-ACK → ACK exchange that establishes a TCP session before data flows. This process synchronizes sequence numbers and confirms bi-directional readiness. A quick memory aid is "SYN starts, SYN-ACK responds, ACK confirms."
Broadcast Domain Fundamentals -
All devices within a broadcast domain receive layer 2 broadcasts, and routers or VLAN boundaries segment these domains to contain traffic. For instance, each router interface creates its own broadcast domain while switches forward ARP requests to all ports. This concept is core to Cisco's CCNA LAN switching curriculum.
Counting Broadcast Domains in Topologies -
Each router interface (or Switched Virtual Interface) and each VLAN equals one broadcast domain. When you refer to the exhibit, tally these interfaces or VLANs to determine "how many broadcast domains are displayed." Practice by sketching simple diagrams and labeling interface counts for clear analysis.
