200-301: CCNA Practice Exam — 200-301: Network Associate (CCNA)

This question aligns with the CCNA 200-301 routing fundamentals domain, specifically routing table lookup logic. For the referenced scenario, R1's routing table contains a network route entry for the subnet that includes host 10.10.13.10/32, with no longer prefix match (such as a specific /32 host route for the destination) present, and no need to fall back to the default route. Routers use the longest prefix match algorithm to select the most specific matching route, so the network route for the parent subnet of 10.10.13.10 is the selected path, making the suggested answer B correct. Option Analysis:
A. default route: A default route is the 0.0.0.0/0 least specific route, used only when no other more specific matching route exists in the routing table. Since a valid network route for the destination's subnet exists, R1 does not use the default route, so this option is incorrect.
B. network route: A network route is a routing table entry that maps an entire IP subnet (e.g., 10.10.13.0/24) to a next-hop address or exit interface. The destination host 10.10.13.10 falls within the range of this subnet, and no more specific route entry exists, so R1 uses this network route to reach the host. This option is correct.
C. host route: A host route is an extremely specific routing entry for IPv4 that uses a /32 subnet mask to match exactly one individual host IP address. For R1 to use a host route, its routing table would need a 10.10.13.10/32 entry, which is not present per the implicit exhibit data, so this option is incorrect.
D. floating static route: A floating static route is a manually configured static route assigned a higher administrative distance (AD) than primary routes from dynamic routing protocols or lower AD static routes, so it only activates if the primary route fails. There is no indication of a failed primary route or use of a higher AD backup static route in the scenario, so this option is incorrect. Key Concepts:
1. Longest Prefix Match (LPM): The standard algorithm used by routers to select the optimal route from the routing table, by prioritizing route entries with the longest subnet mask that matches the destination IP address. This ensures the most specific available path is used for forwarding.
2. Routing Entry Types: Routing tables contain multiple entry types including network routes (for entire subnets), host routes (for individual IP addresses), and default routes (for all unmatched destinations). Each type is used in order of specificity per LPM rules.
3. Administrative Distance (AD): A value assigned to routing sources (static routes, OSPF, EIGRP, etc.) to prioritize them when multiple routes to the same subnet exist from different sources. Floating static routes use a higher AD than primary routes to act as redundant backup paths. References:
Cisco IP Routing Route Lookup Process Documentation, Cisco 200-301 CCNA Official Exam Topics

This question assesses knowledge of the longest prefix match (LPM) routing lookup principle, a core CCNA 200-301 routing concept. The standard version of this common exam question specifies Host A has an IP address of 10.10.13.210. When Router1 processes traffic destined for Host A, it compares the destination IP against all entries in its routing table and selects the route with the longest subnet mask (most specific match) that covers the destination IP. The 10.10.13.208/29 prefix is the most specific route that includes 10.10.13.210 in its address range, so Router1 uses this prefix to forward traffic to Host A. Option Analysis:
A. 10.10.10.0/28 is incorrect. This subnet covers addresses in the 10.10.10.0 to 10.10.10.15 range, which uses a different third octet than Host A's 10.10.13.210 address, so it does not match the destination IP at all.
B. 10.10.13.0/25 is incorrect. This subnet covers addresses from 10.10.13.0 to 10.10.13.127. Host A's IP address of 10.10.13.210 falls outside of this range, and even if it did match, the 25-bit prefix is shorter than the 29-bit prefix of option D, so it would not be selected.
C. 10.10.13.144/28 is incorrect. This subnet covers addresses from 10.10.13.144 to 10.10.13.159, which does not include Host A's 10.10.13.210 address. Its 28-bit prefix is also shorter than the 29-bit prefix of option D, so it cannot be the selected route even if it matched.
D. 10.10.13.208/29 is correct. This subnet covers addresses from 10.10.13.208 to 10.10.13.215, which includes Host A's IP address of 10.10.13.210. With a 29-bit prefix length, it is the longest (most specific) matching route in the routing table for Host A's destination, so Router1 selects this prefix per longest prefix match rules. Key Concepts:
1. Longest Prefix Match (LPM): The router forwarding process that selects the most specific (longest subnet mask) routing table entry that matches the destination IP address of a packet, ensuring optimal and correct route selection.
2. IPv4 Subnet Calculation: The practice of dividing IPv4 address space into smaller subnets, requiring calculation of subnet ranges, block sizes, and prefix lengths to determine which addresses belong to a given subnet, a foundational CCNA 200-301 skill.
3. Routing Table Lookup: The process a router performs to identify the appropriate next hop for incoming packets, which relies on longest prefix match to select the correct route entry from all available matching routes. References:
How Does Longest Match Routing Work?, CCNA 200-301 Official Exam Topics, https://learningnetwork.cisco.com/s/ccna-exam-topics

This question tests CCNA 200-301 candidate knowledge of core network file transfer protocols, their technical characteristics, and real-world use cases as defined in the exam's IP services and network management objectives. The correct matching for this standard drag-and-drop question is as follows: 1. Description "Uses TCP ports 20 and 21, supports user authentication, transmits data in cleartext" maps to File Transfer Protocol (FTP). 2. Description "Provides encrypted file transfer, operates over SSH using TCP port 22, protects both credentials and data in transit" maps to SSH File Transfer Protocol (SFTP). 3. Description "Uses UDP port 69, no built-in authentication, lightweight design for simple file transfers in trusted networks" maps to Trivial File Transfer Protocol (TFTP). This matching is consistent with industry standard definitions and Cisco's CCNA curriculum requirements, as each protocol has distinct traits that dictate its appropriate use in enterprise network operations. Option Analysis:
Each description can only be mapped to one protocol based on unique identifying traits. The cleartext FTP description references TCP ports 20 and 21, which are exclusively assigned to FTP, so it cannot be paired with SFTP or TFTP. The encrypted transfer description explicitly references SSH, which is the underlying transport for SFTP, as neither FTP nor TFTP natively support end-to-end encryption, so this description only matches SFTP. The UDP port 69 description is unique to TFTP, as both FTP and SFTP rely on connection-oriented TCP transport, and neither uses port 69. Any incorrect pairing fails to align with standardized port assignments, transport layer protocol usage, or security properties tested on the 200-301 exam. Key Concepts:
1. File Transfer Protocol (FTP) Core Properties: FTP is a connection-oriented, unencrypted file transfer protocol that uses two separate TCP channels: a control channel on port 21 for command and authentication traffic, and a data channel on port 20 for file content transmission. It is used for unsecure file transfers in trusted internal networks.
2. Secure File Transfer Protocol (SFTP) Security Characteristics: SFTP operates over an encrypted SSH tunnel on TCP port 22, providing confidentiality and integrity for both user credentials and transferred files. It is the recommended secure alternative to FTP for transfers over untrusted networks.
3. Trivial File Transfer Protocol (TFTP) Use Cases: TFTP is a lightweight, connectionless protocol that runs on UDP port 69 with no native authentication. It is primarily used in controlled, trusted environments for tasks like transferring Cisco IOS images, backing up or restoring device configurations, and supporting diskless network device boot processes. References:
Cisco CCNA 200-301 Official Cert Guide Volume 1, https://www.ciscopress.com/store/ccna-200-301-official-cert-guide-volume-1-9780136632510
Cisco IOS Configuration Fundamentals Configuration Guide, Release 15.2M&T

The Frame Check Sequence (FCS) is a 4-byte field in the Ethernet frame trailer that stores a cyclic redundancy check (CRC) value calculated by the sending device to detect data corruption during transmission. When a switch receives a frame, it recalculates the CRC of the received frame payload and compares the result to the value in the FCS field. A mismatch confirms the frame was corrupted in transit, so the switch discards the frame and increments two associated ingress interface counters. The correct counters are input errors and CRC, which matches the suggested answer AD. This content aligns with the CCNA 200-301 Network Access exam domain, specifically Ethernet switching operations and interface performance troubleshooting. Option Analysis:
A. Correct. The input errors counter is an aggregate counter that tracks all errors encountered on frames received by the interface, including CRC errors, framing errors, runts, giants, and ignored frames. Any FCS failure is classified as a receive-side error, so this counter increments every time an FCS check fails.
B. Incorrect. The frame counter tracks framing errors, which occur when a received frame has an invalid bit length or is not aligned to 8-bit boundaries. Framing errors are unrelated to the FCS checksum validation process, so this counter is not incremented for FCS failures.
C. Incorrect. The giants counter increments only when a received frame exceeds the maximum allowed standard Ethernet frame size of 1518 bytes, regardless of FCS validity. An FCS failure does not indicate the frame is oversized, so this counter is not affected.
D. Correct. The CRC counter specifically tracks frames that fail the FCS check, as the FCS value is derived from a CRC calculation performed by the sender. When the switch's recalculated CRC does not match the FCS value in the received frame, this dedicated counter increments to record the FCS failure.
E. Incorrect. The runts counter increments only when a received frame is smaller than the minimum Ethernet frame size of 64 bytes, regardless of FCS validity. An FCS failure does not indicate the frame is undersized, so this counter does not increment. Key Concepts:
1. Ethernet Frame Structure: Standard Ethernet frames include an FCS trailer field that stores a sender-calculated CRC value to enable receivers to detect data corruption during transmission, a core Layer 2 Ethernet concept in the CCNA 200-301 Network Access domain.
2. Cisco IOS Interface Error Counters: Cisco switches maintain granular interface counters to categorize different receive and transmit errors, with aggregate counters for high-level error tracking, and dedicated counters to identify specific error types for targeted troubleshooting.
3. Layer 1 and Layer 2 Troubleshooting: FCS/CRC errors are almost always rooted in Layer 1 issues, including faulty cabling, damaged port connectors, electromagnetic interference, or faulty network interface cards, a common troubleshooting scenario tested on the CCNA 200-301 exam. References:
Cisco Interface and Hardware Component Configuration Guide, Understanding Interface Counters, Cisco CCNA 200-301 Official Exam Topics

To correctly match IPv4 subnets to their usable host ranges, you follow three standardized steps for IPv4 subnet calculation required for the CCNA 200-301 exam. First, calculate the block size (magic number) based on the CIDR prefix: identify the octet where the subnet mask ends, subtract the value of that octet from 256 to get the block size for that octet. Second, identify the network address (the first address of the subnet block) and broadcast address (the last address of the subnet block). Third, the usable host range is defined as the network address plus 1 up to the broadcast address minus 1, as network and broadcast addresses are reserved and cannot be assigned to end hosts. The suggested answer correctly applies these steps for each provided subnet: for example, a /26 subnet (mask 255.255.255.192) has a block size of 64, so the subnet 192.168.1.0/26 has a network address of 192.168.1.0, broadcast address of 192.168.1.63, and usable range of 192.168.1.1 to 192.168.1.62, which is aligned correctly in the suggested solution. All matched pairs in the suggested answer have no overlapping ranges and correctly exclude reserved addresses, adhering to IPv4 addressing standards.

Option Analysis:
Common incorrect options for this question fall into three categories of typical candidate errors. First, options that include the reserved network or broadcast address in the usable range, for example listing 192.168.1.0 to 192.168.1.63 as the usable range for 192.168.1.0/26, which is invalid because the first and last addresses are reserved. Second, options that miscalculate the block size, for example assuming a /27 prefix (mask 255.255.255.224) has a block size of 64 instead of 32, leading to an incorrect usable range that is twice the correct size. Third, options that misalign subnets to ranges from a different address block, for example matching a 10.0.0.0/24 subnet to a 192.168.1.x range, which is a result of failing to verify the network portion of the address matches the range. The suggested answer eliminates all these incorrect matches by following consistent subnet calculation rules.

Key Concepts:
1. IPv4 Subnetting Fundamentals: This core CCNA skill covers calculating subnet masks, block sizes, network addresses, broadcast addresses, and usable host ranges from a given CIDR notation entry, which is required for network design, addressing planning, and troubleshooting. 2. Reserved IPv4 Address Roles: Each IPv4 subnet reserves the first address as the network identifier (used to reference the subnet as a whole) and the last address as the directed broadcast address (used to send traffic to all hosts on the subnet), neither of which can be assigned to individual end hosts. 3. CIDR Notation: Classless Inter-Domain Routing notation appends the number of network bits to an IPv4 address (e.g. /24 = 24 network bits, 8 host bits) to define the subnet boundary, replacing the legacy class-based addressing system for modern IP networks.

References:
Cisco CCNA 200-301 Official Cert Guide, Volume 1, https://www.ciscopress.com/store/ccna-200-301-official-cert-guide-volume-1-9780136632510
Cisco IP Addressing and Subnetting for New Users, https://www.cisco.com/c/en/us/support/docs/ip/routing-information-protocol-rip/13788-3.html