Cisco CCNA Cisco CCNA (200-301) Practice Test 2025

The correct answer is (b) Layer 2 - Data Link. Switches operate primarily at Layer 2 (Data Link layer) of the OSI model. They use MAC (Media Access Control) addresses to make forwarding decisions. When a switch receives a frame and the destination MAC address is not found in its MAC address table (also called the CAM table), it floods the frame out all ports except the port on which it was received. This is a Layer 2 operation known as unknown unicast flooding. Layer 1 (Physical) deals with electrical signals, cables, and physical connectivity. Layer 3 (Network) involves IP addressing and routing decisions made by routers. Layer 4 (Transport) handles end-to-end communication using TCP or UDP protocols. The flooding behavior described is specifically a Layer 2 switching function.

The correct answer is (c) 255.255.255.224 (/27) with 32 total addresses. To support exactly 30 usable host addresses, you need to determine the smallest subnet that provides at least 30 hosts. The formula for usable hosts is 2^n - 2, where n is the number of host bits. With 5 host bits: 2^5 - 2 = 30 usable hosts, and 2^5 = 32 total addresses. A /27 subnet mask (255.255.255.224) leaves 5 bits for host addressing (32 - 27 = 5 host bits), providing exactly 30 usable addresses and 32 total addresses (including the network address and broadcast address). A /28 mask (255.255.255.240) would only provide 2^4 - 2 = 14 usable hosts, which is insufficient. A /26 mask (255.255.255.192) would provide 2^6 - 2 = 62 usable hosts, which wastes address space. A /25 mask (255.255.255.128) would provide 2^7 - 2 = 126 usable hosts, which is far more than needed.

The correct answer is (d) IP routing must be enabled on the Layer 3 switch using the 'ip routing' global configuration command. VLANs create separate broadcast domains at Layer 2, which means hosts in different VLANs cannot communicate directly. For inter-VLAN routing, a Layer 3 device must route packets between the VLANs. When using SVIs (Switch Virtual Interfaces) on a Layer 3 switch, the switch can perform the routing function itself. However, Layer 3 switches have IP routing disabled by default. The 'ip routing' command must be entered in global configuration mode to enable the routing engine on the switch, allowing it to route packets between VLAN 10 and VLAN 20 using the SVI IP addresses as gateways. A trunk link between the switch and itself is not needed since both VLANs exist on the same switch. Placing both hosts in the same VLAN would defeat the purpose of VLAN segmentation. A static route to 0.0.0.0/0 is for default routing to external networks, not for local inter-VLAN routing where the switch already has directly connected SVI interfaces.

The correct answer is (b) Path 2 with a total cost of 2. OSPF uses a cost metric based on interface bandwidth to determine the best path. The cost of a path is the sum of the costs of all links along that path. OSPF selects the path with the lowest total cost. Path 1 has a total cost of 1 + 10 = 11. Path 2 has a total cost of 1 + 1 = 2. Path 3 has a total cost of 100. Since Path 2 has the lowest total cost of 2, OSPF will install this path in the routing table. OSPF is a link-state routing protocol that uses Dijkstra's Shortest Path First algorithm to calculate the best (lowest cost) path to each destination. OSPF only performs equal-cost load balancing, meaning it will load-balance across paths that have the same total cost, not across paths with different costs.

The correct answer is (c) 802.11ax (Wi-Fi 6). IEEE 802.11ax, marketed as Wi-Fi 6, operates in both the 2.4 GHz and 5 GHz bands and introduces key technologies for dense environments: MU-MIMO (supporting up to 8 simultaneous spatial streams in both uplink and downlink), OFDMA (Orthogonal Frequency-Division Multiple Access) for efficient spectrum sharing among multiple clients, BSS Coloring to reduce co-channel interference, and Target Wake Time (TWT) for improved power efficiency. It provides theoretical maximum speeds of approximately 9.6 Gbps. 802.11ac (Wi-Fi 5) operates only in the 5 GHz band (not 2.4 GHz) and supports MU-MIMO only in the downlink direction. 802.11n (Wi-Fi 4) operates in both bands but only supports SU-MIMO (single-user MIMO), not MU-MIMO. 802.11g operates only in the 2.4 GHz band, does not support MIMO at all, and has a maximum speed of only 54 Mbps.

The correct answer is (a) access-list 100 deny tcp 192.168.1.0 0.0.0.255 host 10.0.0.100 eq 80, then access-list 100 permit ip any any. Extended ACLs (numbered 100-199) can filter traffic based on source address, destination address, protocol, and port number. The deny statement uses: 'tcp' as the protocol (HTTP uses TCP); '192.168.1.0 0.0.0.255' as the source network with wildcard mask (0.0.0.255 is the wildcard for /24, matching all hosts in the 192.168.1.0 network); 'host 10.0.0.100' as the specific destination server; and 'eq 80' to match destination port 80 (HTTP). The second line 'permit ip any any' allows all other traffic, which is necessary because Cisco ACLs have an implicit 'deny all' at the end. Without this permit statement, all traffic would be blocked. Option (b) uses a standard ACL (number 10), which cannot filter by destination address or port. Option (c) uses the wrong wildcard mask (255.255.255.0 would match any network). Option (d) is missing the permit statement, so the implicit deny would block all traffic.

The correct answer is (a) GET. In RESTful API design, the HTTP GET method is used to retrieve (read) a resource from the server without modifying it. When a network engineer wants to read the running configuration, they send a GET request to the appropriate API endpoint (e.g., /api/v1/devices/{id}/config). A successful response returns HTTP status code 200 (OK) along with the requested data, typically in JSON or XML format. POST is used to create a new resource on the server (e.g., creating a new VLAN or user account). PUT is used to update or replace an existing resource entirely. DELETE is used to remove a resource from the server. These HTTP methods map to the CRUD (Create, Read, Update, Delete) operations: POST = Create, GET = Read, PUT = Update, DELETE = Delete.

The correct answer is (b) Discover, Offer, Request, Acknowledge (DORA). The DHCP lease process follows the four-step DORA sequence: (1) DHCP Discover - the client broadcasts a message to find available DHCP servers on the network; (2) DHCP Offer - one or more DHCP servers respond with an IP address offer, including the proposed IP address, subnet mask, default gateway, DNS servers, and lease duration; (3) DHCP Request - the client broadcasts a request accepting one of the offers (broadcasting so all DHCP servers know which offer was accepted); (4) DHCP Acknowledge - the selected DHCP server sends a final acknowledgment confirming the lease, and the client configures its network interface with the provided settings. This DORA process uses UDP ports 67 (server) and 68 (client). The Discover and Request messages are broadcast by the client, while the Offer and Acknowledge messages are sent by the server.

The correct answer is (c) Enforcing network policies, performing inter-VLAN routing, filtering traffic with ACLs, and aggregating connections from the access layer. In the Cisco three-tier hierarchical model, each layer has a distinct role. The distribution layer serves as the policy enforcement point, sitting between the access layer and the core layer. Its primary functions include: routing between VLANs (inter-VLAN routing), applying access control lists (ACLs) and quality of service (QoS) policies, aggregating uplinks from multiple access layer switches, and providing redundant connections to the core layer. The access layer (not described in the correct answer) provides direct connectivity to end-user devices, implementing port security, 802.1X authentication, and PoE. The core layer provides high-speed backbone transport between distribution layer switches with minimal latency and should avoid complex policy processing. Providing direct connectivity to end-user devices is the function of the access layer, not the distribution layer.

The correct answer is (d) UDP, because it provides lower latency by avoiding connection setup and retransmission overhead, which is acceptable for real-time streaming where occasional packet loss is preferable to delays. UDP (User Datagram Protocol) is a connectionless transport layer protocol that does not establish a session before sending data (no three-way handshake), does not guarantee delivery (no acknowledgments or retransmissions), does not guarantee packet ordering, and has a minimal 8-byte header (compared to TCP's 20-byte minimum header). For real-time video streaming, occasional lost packets result in minor visual artifacts, which are far less disruptive than the delays caused by TCP's retransmission mechanism. When TCP detects a lost segment, it must retransmit it and potentially wait for reordering, which introduces latency that is unacceptable for real-time media. TCP is preferred for applications where data integrity is critical, such as file transfers, web browsing, and email.