H12-811_V2.0 HCIA-Datacom V2.0 Questions and Answers

In the standard TCP/IP forwarding model, transport-layer headers such as TCP and UDP headers are added by the source host and are mainly interpreted by the destination host. Routers that forward packets between the source and destination operate primarily at the network layer , using the destination IP address in the IP header to make forwarding decisions. Therefore, under normal routing behavior, routers do not process transport-layer header information when deciding how to forward packets.

This is a key concept in layered communication. The source host encapsulates application data with a transport-layer header, then with an IP header, and finally with a data-link header. Each router along the path removes only the Layer 2 frame header, checks the Layer 3 destination IP information, decrements TTL, recalculates the IP header checksum when required, and forwards the packet. The transport-layer content remains unchanged in normal forwarding. HCIA-Datacom uses this principle to explain end-to-end communication and layer responsibilities. Although advanced devices may inspect higher-layer information for security or policy purposes, standard router forwarding in the basic TCP/IP model does not depend on transport-layer processing.

On Huawei devices, the undo command is used to remove a previously applied configuration, disable a function, or restore a parameter to its default state. In option B , undo ip address is a valid interface-view command that removes the IP address configured on the interface. In option C , undo portswitch is also a valid interface command on switch interfaces that converts a Layer 2 interface into a Layer 3 interface when supported by the device. In option D , undo sysname restores the device name to the default hostname, which is valid in system view.

Option A is incorrect because system-view is a command used to enter system view from user view, but undo system-view is not a valid command for exiting that view. Exiting system view is done with commands such as quit, return, or by using shortcut keys. This question checks the understanding that undo only applies to configurable features and parameters, not to view-switching commands in the CLI hierarchy.

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This statement is true . ARP is a Layer 2 broadcast-based protocol used to resolve an IPv4 address into a MAC address within the same broadcast domain. If two PCs are connected to the same switch but cannot learn each other’s ARP entries, one likely reason is an incorrect VLAN configuration .

For example, if PC1 and PC2 are placed in different VLANs, or if one interface is configured with the wrong access VLAN, ARP broadcast frames from one PC will not reach the other PC because VLANs separate Layer 2 broadcast domains. As a result, the ARP request will not be received by the peer, and the MAC address cannot be resolved. Other causes may also exist, such as incorrect IP addressing, port isolation, or security policies, but VLAN misconfiguration is a very common and valid cause in campus switching scenarios. HCIA-Datacom teaches that ARP communication depends on correct Layer 2 domain membership, and VLAN planning or interface configuration errors often directly affect host-to-host communication even when both hosts are physically connected to the same switch.

In TCP, the acknowledgment number indicates the next byte that the receiver expects to receive. In the figure, PC1 sends a TCP segment to PC2 with sequence number = a+22 and payload length = 22 bytes . Since TCP sequence numbers count bytes, the last byte carried in this segment corresponds to sequence number a+43 . Therefore, after PC2 successfully receives this data, it sends back an ACK indicating that the next expected byte is a+44 .

That is why option B is correct. This is a standard TCP reliability mechanism. TCP does not acknowledge “packets” as units; it acknowledges the byte stream. The ACK number always points to the next byte expected from the peer. The source and destination port numbers identify the session, but the sequence and acknowledgment numbers track ordered delivery. HCIA-Datacom uses this mechanism to explain connection-oriented transport, reliable delivery, retransmission, and traffic control. Understanding how the payload length affects sequence progression is essential when analyzing packet captures and troubleshooting TCP communication problems in enterprise networks.

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This statement is false . On Huawei devices, the domain to which a user belongs is usually determined by the domain part carried in the user name, for example user@huawei.com. However, if the specified domain is not configured on the NAS device, authentication does not necessarily fail immediately . In many cases, the device can use a default domain for authentication processing, depending on the AAA configuration.

Huawei AAA supports both an administrator user default domain and a normal user default domain . If a user name does not match a configured domain, or the domain carried in the user name is unavailable, the device may fall back to the default domain and continue authentication according to the configured policy. Therefore, the statement is incorrect because it treats authentication failure as unavoidable in every such case. HCIA-Datacom emphasizes domain-based AAA processing because it allows different groups of users to use different authentication, authorization, and accounting methods. At the same time, learners must understand the function of default domains, which provide flexibility in real deployments and prevent unnecessary authentication failures in some login scenarios.

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In IPv6, link-local addresses use the prefix FE80::/10 . These addresses are automatically generated or configured for communication on the local link only and are not routed across Layer 3 boundaries. Therefore, among the given options, FE80::FA63:DBFF:FE9E:10 is the correct link-local address, making option C correct.

Options A and B belong to the Unique Local Address (ULA) space, which uses the prefix FC00::/7 . These addresses are intended for private internal IPv6 networks, somewhat similar in purpose to private IPv4 address ranges, but they are not link-local addresses. Option D , which starts with 2001::, is a global unicast address , used for routable communication across IPv6 networks. HCIA-Datacom teaches that link-local addresses are essential in IPv6 because they are used for functions such as neighbor discovery, router discovery, and routing protocol communication on the local segment. Even when a device has global unicast addresses, the link-local address still plays an important role in normal IPv6 operation and protocol adjacency establishment.

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A /27 subnet mask is 255.255.255.224, which means each subnet contains 32 IP addresses. The subnet increments in blocks of 32 in the last octet: 0, 32, 64, 96, 128, 160, 192, 224. The address 192.168.1.200/27 belongs to the subnet 192.168.1.192/27.

For this subnet, the network address is 192.168.1.192, the broadcast address is 192.168.1.223, and the valid host range is from 192.168.1.193 to 192.168.1.222. Therefore, 192.168.1.221/27, 192.168.1.193/27, and 192.168.1.222/27 are all valid host addresses in the same subnet and are reachable at Layer 2 without routing. That makes A, C, and D correct.

Option B is not correct because 192.168.1.192/27 is the network address of the subnet and cannot be assigned to a host by default. This question checks IP subnetting and the ability to identify valid hosts within the same broadcast domain.

All four statements are correct. The code uses the Paramiko library to automate SSH login to a network device. import paramiko and import time load the Python modules required for SSH communication and delay control, so option C is correct. The statement ssh = paramiko.SSHClient() creates an SSH client object, and ssh.set_missing_host_key_policy(paramiko.AutoAddPolicy()) allows the client to accept an unknown host key automatically in this example scenario.

The command ssh.connect('192.168.1.254', username='python', password='Huawei@123') establishes an SSH connection to the target device, so option B is correct. Then channel = ssh.invoke_shell() opens an interactive shell channel , which is commonly used to send CLI commands and receive output just as an administrator would in a terminal session, making option D correct. The command channel.send('screen-length 0 temporary\n') disables page-by-page output for the current session, which is useful in network automation. Finally, ssh.close() closes the SSH session and releases the connection, so option A is correct. HCIA-Datacom automation knowledge often uses Paramiko examples to demonstrate basic Python-based device O & M.

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The protocol that cannot directly modify device configurations such as interface IP addresses or device names is SFTP , so option C is correct. SFTP is a secure file transfer protocol that runs over SSH and is mainly used to upload, download, and manage files between a client and a network device. It is commonly used for tasks such as transferring configuration files, system software, patches, or log files, but it does not itself provide an interactive or structured configuration modification mechanism.

By contrast, STelnet allows secure remote CLI login, through which an administrator can directly enter commands to change device settings. NETCONF is specifically designed for network configuration management and can modify configurations in a structured manner. SNMP can also modify certain managed object values through write operations when permissions and MIB support allow it, although in practice it is used more often for monitoring. HCIA-Datacom distinguishes between management-plane protocols based on their roles: interactive access, structured configuration, monitoring, and file transfer. This question checks whether the learner can identify SFTP as a file transfer tool rather than a direct configuration protocol.

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Comprehensive and Detailed 150 to 200 words of Explanation From Datacom knowledge:

The false statement is B . From the AAA configuration output, the value of Remote-admin-user block time is clearly shown as 5 Min(s) , which means the account lockout duration is 5 minutes , not 30 minutes.

Option A is true because Remote-admin-user block retry-time : 3 indicates that after 3 consecutive authentication failures , the account will be blocked. Option C is also true because the displayed Domain Name Delimiter is @ , which is the separator used in usernames such as user@huawei.com. Option D is true as well because the output shows Local-user : total: 512 used: 2 , meaning that the device supports a maximum of 512 local users , and currently 2 local users have been created.

This question checks the ability to correctly read AAA configuration output on Huawei devices. In HCIA-Datacom knowledge, it is important to distinguish between retry interval , retry count , and block time , because these values represent different security control parameters and are often confused during troubleshooting or configuration review.

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For two directly connected edge networks to communicate through intermediate routing, each end router must have a route to the remote destination network pointing to the correct next hop on the transit link. Since 10.0.0.0/24 is directly connected to R1 and 20.1.1.0/24 is directly connected to R3, R1 needs a route to 20.1.1.0/24, and R3 needs a route to 10.0.0.0/24.

Option A is correct because it configures on R1 a static route to the remote network 20.1.1.0/24 using next hop 10.0.0.2, which is the neighbor toward the transit path. Option D is correct because it configures on R3 a static route to the remote network 10.0.0.0/24 using next hop 20.1.1.1, which is the proper adjacent forwarding address in that direction. Option B is incorrect because a router cannot use a next hop that belongs to the remote destination network but is not directly reachable as a valid immediate forwarding address in this topology. Option C is also incorrect because the specified next hop is not the correct adjacent next-hop address for R3. HCIA-Datacom stresses that static routes must always point to a reachable next hop or outbound interface.

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After STP convergence, only ports in the forwarding state participate in active traffic forwarding, while redundant ports may be placed into the blocking or discarding state to eliminate loops. According to the topology and STP role election shown in the question, the valid forwarding path from SW1 to SW4 is SW1 → SW3 → SW4, so option B is correct.

This means that the direct alternative path or the path through SW2 is not the active spanning-tree forwarding path after election and state transition. STP selects paths based on the root bridge, path cost, bridge ID, and port ID. Once the root bridge and port roles are determined, some links remain active and others are blocked to ensure a loop-free Layer 2 topology. HCIA-Datacom emphasizes that the resulting forwarding topology is a tree, not a mesh, even if the physical topology contains redundant links. Understanding the actual forwarding path after STP convergence is important for troubleshooting connectivity, predicting traffic behavior, and verifying whether bridge priority and path-cost settings have produced the intended design outcome in campus switching networks.

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The correct answer is C. In the command output, the AP state is shown as ver-mismatch. This state directly indicates a version mismatch between the AP and the WAC. In Huawei WLAN deployment, a Fit AP must use a software version that is compatible with the WAC version. If the versions do not match, the AP may be discovered by the WAC and appear in the AP list, but it cannot successfully complete the online process.

Option A is incorrect because blacklist-related failures are displayed with blacklist-related status information, not ver-mismatch. Option B is also incorrect because authentication failures normally generate authentication-related fault indications. Option D is incorrect because configuration initialization failure would not be identified by the specific ver-mismatch state.

HCIA-Datacom troubleshooting knowledge emphasizes reading AP online states carefully. Common causes of AP online failure include IP address acquisition failure, CAPWAP tunnel establishment failure, insufficient licenses, authentication problems, and version mismatch. When the state explicitly shows ver-mismatch, the troubleshooting direction is clear: check AP and WAC software compatibility and upgrade or align the software version as needed.

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This statement is false . In classic STP, when a non-root switch detects a topology change, it does not continuously send configuration BPDUs upstream to notify the root bridge. Instead, it sends a Topology Change Notification (TCN) BPDU toward the root bridge through its root port. Each upstream switch acknowledges the TCN and forwards it further until it reaches the root bridge.

After the root bridge receives the topology change notification, the root bridge sets the Topology Change (TC) flag in its configuration BPDUs, and those configuration BPDUs are then propagated throughout the network. Therefore, topology-change notification and normal configuration BPDU transmission are different functions. The statement is wrong because it confuses TCN BPDUs with configuration BPDUs , and also inaccurately describes the notification behavior. HCIA-Datacom requires learners to distinguish between these BPDU types and understand how STP reacts to topology changes by accelerating MAC address aging and informing the network through the root bridge. This process helps the Layer 2 topology converge and reduces long-lasting forwarding inconsistencies after a link or port-state change.

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During modulation, the transmitter maps digital information onto certain physical characteristics of a carrier signal so that the information can be transmitted over the air. The three classic carrier parameters that can be modified are amplitude , frequency , and phase . Therefore, options A , B , and D are correct.

Amplitude modulation changes the strength of the carrier wave. Frequency modulation changes the oscillation rate of the carrier. Phase modulation changes the phase angle of the carrier relative to a reference. Modern wireless communication systems often combine these parameters, especially amplitude and phase, in complex digital modulation schemes such as QPSK, 16-QAM, 64-QAM, or higher-order QAM used in WLAN standards. Option C , channel, is not a carrier parameter modified during modulation. A channel refers to a frequency resource or spectrum allocation used for communication, not a physical waveform characteristic being directly altered to encode bits. HCIA-Datacom introduces these basic wireless concepts to help learners understand how WLAN signals are transmitted, how data rate improvements are achieved, and why different modulation methods have different requirements for signal quality and interference resistance.

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