Huawei h12-821 practice test

Answer:

Explanation:
The hardware modules of Huawei modular devices and their functions are:
Main Processing Unit (MPU): Provides control and management planes for the entire system,
responsible for protocol processing, system security, and software upgrades.
Switch Fabric Unit (SFU): Provides the data plane, enabling high-speed data switching between
service modules.
Line Processing Unit (LPU): Manages data forwarding, offering various interfaces (optical and
electrical) for data access​​.

Answer:

B

Explanation:
The question indicates that a router performs a lookup in its FIB table for a packet and determines
that the tunnel ID in the matching entry is 0, suggesting that the packet needs to be forwarded
through a tunnel such as an MPLS tunnel. However, this is a misunderstanding of the FIB
functionality.
FIB Table Overview
The Forwarding Information Base (FIB) is used to make packet-forwarding decisions. Entries in the
FIB include next-hop information, which can be directly linked to an interface or a tunnel.
If the Tunnel ID is 0, it indicates that the packet is forwarded via a normal routing path and not
through a tunnel.
For MPLS or other tunnels, the Tunnel ID would have a non-zero value pointing to the associated
tunnel.
MPLS Tunnel Operation
When a router forwards packets through an MPLS tunnel, a label-switched path (LSP) is set up. The
FIB would reflect specific tunnel identifiers for packets that need such encapsulation.
HCIP-Datacom-Core Reference
Routing Principles and MPLS​explain the forwarding mechanisms clearly, stating that if a packet is
routed normally, the tunnel ID remains 0.
The section on MPLS​clarifies the encapsulation process and the role of tunnel identifiers.
Hence, the claim in the question is incorrect. A Tunnel ID of 0 implies no tunneling is required, and
normal IP forwarding occurs

Answer:

B

Explanation:
The scenario describes a mismatch in OSPF network types between two connected routers: one set
to Point-to-Point (P2P) and the other set to Point-to-Multipoint (P2MP). While aligning Hello
intervals may seem sufficient for establishing an OSPF neighbor relationship, the fundamental
mismatch in network types introduces issues.
OSPF Network Types
P2P: Assumes a direct connection with a single neighbor, uses faster convergence and simpler LSDB
synchronization.
P2MP: Supports multiple neighbors on a single interface, requiring different handling for DR/BDR
roles and LSDB updates.
Impact of Network Type Mismatch
If Hello intervals are aligned, adjacency establishment might occur. However, mismatched network
types affect neighbor role assignment and LSDB synchronization.
P2P expects a direct link and would handle updates differently than P2MP, which assumes multiple
neighbors. This leads to inconsistencies in route calculation and forwarding.
HCIP-Datacom-Core Reference
OSPF Basics and Configuration​clearly outlines the criticality of consistent network type configuration
for stable OSPF operation.
Lab examples in the HCIP Datacom Lab Guide​further demonstrate the consequences of such
mismatches, including unstable neighbor states and incomplete LSDB synchronization.
Hence, the statement that neighbor relationships and LSDB synchronization remain unaffected is
incorrect. Proper OSPF operation requires matching network types in addition to aligned Hello
intervals.

Answer:

A

Explanation:
When OSPF routers have interfaces on different network segments with different subnet masks, the
network type can be adjusted to establish adjacency. A point-to-point (P2P) network type eliminates
the requirement for matching subnet masks by treating the link as directly connected without
intermediate devices.
P2P Network Characteristics
OSPF treats the link as a direct connection between two routers.
No DR/BDR election occurs, simplifying adjacency establishment.
Subnet mask differences do not hinder neighbor relationships as the link is viewed as a logical
tunnel.
HCIP-Datacom-Core Reference
The OSPF configuration section explicitly mentions P2P as a suitable network type for resolving
adjacency issues caused by mismatched subnet masks​​.

Answer:

A, B, C,D

Explanation:
​ OSPF Area Design and Loop Prevention:
OSPF uses a hierarchical structure with areas to improve scalability and efficiency. Area 0, the
backbone area, plays a crucial role in ensuring loop-free route distribution between areas. The
following mechanisms are key to preventing routing loops:
Strict adherence to hierarchical area design.
Prohibition of direct inter-area route exchanges between non-backbone areas.
Reference: HCIP-Datacom-Core Technology Training Material (OSPF Basics and Advanced Concepts)​​.
​ Analysis of Each Statement:
A . Inter-area routes cannot be directly transmitted between non-backbone areas.
This statement is TRUE. OSPF mandates that all inter-area routing must pass through Area 0. Direct
inter-area route exchanges between two non-backbone areas are not allowed to prevent loops.
Reference: HCIP-Datacom-Core Technology Training Material (Inter-Area Routing Mechanisms)​.
B . All non-backbone areas must be directly connected to area 0.
This statement is TRUE. OSPF requires every non-backbone area to connect directly to Area 0 to
facilitate loop-free inter-area routing. Virtual links may be configured in exceptional cases where
direct connection is not possible.
Reference: HCIP-Datacom-Core Technology Training Material (OSPF Backbone and Area
Connectivity)​​.
C . Inter-area routes need to be forwarded through area 0.
This statement is TRUE. All inter-area traffic must traverse Area 0 to ensure hierarchical routing and
loop prevention. This rule is a core design principle of OSPF.
Reference: HCIP-Datacom-Core Technology Training Material (Routing Control and Loop Prevention
in OSPF)​​.
D . An ABR cannot inject Type 3 LSAs that describe routes to a network segment in an area back to
the same area.
This statement is TRUE. OSPF explicitly prohibits an ABR from injecting Type 3 LSAs describing a route
into the same area where the route originates. This mechanism prevents routing loops within an
area.
Reference: HCIP-Datacom Advanced Routing & Switching Technology (OSPF LSA Types and ABR
Behavior)​.
​ Conclusion:
All options (A, B, C, D) are correct. OSPF enforces a robust loop prevention mechanism through
hierarchical routing, mandatory traversal via Area 0, and strict rules on LSA propagation by ABRs. This
ensures reliable and loop-free inter-area routing in OSPF networks.

Answer:

C

Explanation:
​ OSPF Authentication Overview
The Auth Type field in the OSPF packet header determines the authentication mode. If the Auth Type
is 1, plaintext authentication is used.
Plaintext authentication involves transmitting the password in an easily readable format, which is
less secure compared to MD5.
​ HCIP-Datacom-Core Reference
Authentication mechanisms, including plaintext authentication, are detailed in the OSPF security
configuration chapter, confirming that Auth Type = 1 corresponds to plaintext​​.

Answer:

B

Explanation:
​ OSPF LSA Flooding Mechanism
If a router receives an LSA identical to one already in its LSDB, it does not flood the LSA again unless
the LSA has changed (i.e., the sequence number or content has been updated).
OSPF ensures efficient use of bandwidth by avoiding redundant flooding of unchanged LSAs.
​ HCIP-Datacom-Core Reference
The OSPF LSDB synchronization process explains that unchanged LSAs are not reflooded, ensuring
stability and resource optimization​​.

Answer:

A

Explanation:
​ OSPF Authentication Overview
OSPF supports three authentication modes:
Null Authentication: No authentication (default).
Plaintext Authentication: Uses clear-text passwords.
MD5 Authentication: Secure cryptographic authentication.
​ Interface-Level Priority
When both interface-level and area-level authentication are configured, OSPF prioritizes interface-
level authentication. This ensures that interface-specific security overrides area-wide configurations
for greater granularity and security.
​ HCIP-Datacom-Core Reference
OSPF authentication hierarchy and configurations are detailed in the OSPF security configuration
chapter​.

Answer:

C

Explanation:
​ Silent Interface Explanation
The silent-interface command is used to prevent OSPF from sending or receiving OSPF packets on the
specified interface (GE 0/0/1). This disables OSPF adjacency establishment and stops route
advertisement for that interface.
​ Network Observations
Statement A: R2 can access the server.
This is correct, as the silent interface does not impact data traffic, only OSPF-related communication.
Statement B: GE 0/0/1 of R1 cannot send OSPF packets.
Correct due to the silent-interface configuration.
Statement C: The network segment to which GE 0/0/1 of R1 belongs cannot be advertised.
This is correct, as the silent interface prevents route advertisement.
Statement D: GE 0/0/1 of R1 cannot accept OSPF packets.
Correct, as the silent interface configuration blocks packet reception.
​ HCIP-Datacom-Core Reference
OSPF interface command behavior is outlined in the configuration and lab examples sections​​.

Answer:

A

Explanation:
​ Understanding Router ID and Its Role in OSPF:
In OSPF, the Router ID uniquely identifies a router within the OSPF domain. If two routers are
configured with the same Router ID, it can lead to issues such as LSA conflicts and flapping. This is
because the Router ID is used as a key in OSPF operations, including LSA generation and database
synchronization.
Reference: HCIP-Datacom-Core Technology Training Material (OSPF Basics - Router ID and LSA
Handling)​.
​ Scenario Details:
Different Areas: Even if the two routers belong to different areas, the Router ID remains globally
significant in the OSPF domain. This means that any duplication of Router IDs will confuse OSPF
mechanisms.
ASBR (Autonomous System Boundary Router): When one of the routers is an ASBR, it generates Type
4 and Type 5 LSAs to describe external routes. These LSAs use the Router ID as an identifier. If
another router in the network has the same Router ID, conflicts occur during LSDB synchronization.
Reference: HCIP-Datacom Advanced Routing & Switching Technology (LSA Types and ASBR
Operations)​​.
​ Impact of Router ID Duplication:
LSA Flapping: The OSPF process receives conflicting LSAs from routers with the same Router ID. This
results in continuous updates and withdrawals of these LSAs, causing flapping.
Routing Instability: LSA flapping leads to frequent recalculations of the OSPF shortest path tree (SPT),
affecting overall network stability.
Reference: HCIE-Datacom V1.0 Training Material (OSPF Troubleshooting and Best Practices)​​.
​ Conclusion:
The statement is TRUE. LSA flapping occurs when two routers in an OSPF network have the same
Router ID, even if they are in different areas and one is an ASBR. This is due to the global significance
of Router IDs in OSPF and the role they play in LSA generation and propagation.

Answer:

B

Explanation:
​ LSA Lifetime and Deletion
The LS Age field in the LSA header tracks the age of an LSA. When the LS Age reaches its maximum
value (3600 seconds), the LSA is marked for deletion. This ensures old or stale LSAs are removed from
the network to maintain accurate routing information.
​ HCIP-Datacom-Core Reference
Detailed explanation of LS Age behavior and LSA deletion processes can be found in the OSPF LSDB
and LSA sections​​.

Answer:

Explanation:
Network Types and Corresponding Link Layer Protocols
Broadcast: Ethernet
Point-to-Point (P2P): PPP, HDLC
Point-to-Multipoint (P2MP): PPP
Non-Broadcast Multi-Access (NBMA): Frame Relay
​ OSPF Network Types:
OSPF classifies networks based on link layer protocols into the following types:
Broadcast: This type assumes that all routers on the network can communicate directly with one
another using multicast or broadcast frames. Ethernet networks are typical examples.
Point-to-Point (P2P): This type is used for links that connect two routers directly. Common protocols
include PPP (Point-to-Point Protocol) and HDLC.
Point-to-Multipoint (P2MP): This type simulates multiple point-to-point connections over a single
physical network, often used in WAN scenarios where PPP is employed.
Non-Broadcast Multi-Access (NBMA): These networks connect multiple devices but lack native
broadcast capability, such as Frame Relay.
Reference: HCIP-Datacom-Core Technology Training Material (OSPF Network Types)​​.
​ Explanation of Matches:
Broadcast - Ethernet: Ethernet supports broadcast and multicast communication, making it a suitable
example of a broadcast OSPF network.
P2P - PPP, HDLC: Both PPP and HDLC are designed for direct communication between two nodes,
fitting the P2P category.
P2MP - PPP: In WANs, PPP often operates in a point-to-multipoint configuration, simulating separate
connections for each endpoint.
NBMA - Frame Relay: Frame Relay is a classic NBMA technology where direct communication
between devices requires manual configuration, as there is no inherent broadcast capability.
​ Conclusion:
This classification ensures that OSPF operates efficiently over different network types by adapting
neighbor discovery and LSA propagation mechanisms to the underlying link layer technology.

Answer:

A, B, D

Explanation:
​ LSP Generation in IS-IS
IS-IS routers generate new Link State Packets (LSPs) under the following conditions:
Interface Status Changes: When IS-IS interfaces go up or down, the link state changes, triggering LSP
updates.
Periodic Updates: IS-IS periodically regenerates LSPs to ensure link-state information remains
synchronized across the network.
Interface Metric Changes: Any modification to interface costs results in a new LSP to reflect the
updated cost in the network.
​ Incorrect Option
C . Inter-area IP routes change is incorrect because IS-IS does not inherently differentiate between
areas for LSP generation.
​ HCIP-Datacom-Core Reference
IS-IS LSP generation rules are detailed in the IS-IS configuration and implementation chapters​​.

Answer:

A

Explanation:
​ DIS and DR Election
The IS-IS Designated Intermediate System (DIS) is responsible for generating and updating
pseudonode LSPs on a broadcast network.
Unlike OSPF DR, the IS-IS DIS does not preempt by default. This behavior avoids unnecessary flapping
in the network due to frequent DIS re-elections.
​ HCIP-Datacom-Core Reference
The characteristics of DIS and DR behavior are explained in IS-IS network operation chapters​​.

Answer:

A, B, C

Explanation:
​ IS-IS Overview: Intermediate System to Intermediate System (IS-IS) is a link-state routing protocol.
Routers exchange Link State Packets (LSPs) to maintain a synchronized link-state database. These LSPs
are categorized into Level-1 LSPs (intra-area routing) and Level-2 LSPs (inter-area routing). Both types
share the same packet format.
Reference: HCIP-Datacom-Core Technology Training Material (IS-IS LSPs and Packet Structure)​​.
​ LSP ID Format: The LSP ID uniquely identifies each LSP and ensures accurate routing information. It
comprises the following components:
System ID (C): A 6-byte identifier assigned to each router, derived from the router's NET (Network
Entity Title). This identifier ensures unique identification of routers within the IS-IS domain.
Pseudonode ID (B): Assigned when a router acts as a Designated Intermediate System (DIS) on a
broadcast network. It differentiates LSPs generated by the DIS from other routers.
LSP Number (A): A 1-byte field indicating the sequence number of the LSP. It helps distinguish
multiple LSPs generated by the same router for the same level.
Reference: HCIP-Datacom Advanced Routing & Switching Technology (IS-IS LSP Format)​​.
​ IS Type Exclusion:
IS Type (D) is not part of the LSP ID itself. It is a field within the IS-IS PDU that indicates the type of
Intermediate System (Level-1, Level-2, or both) but does not contribute to the composition of the
LSP ID.
Reference: HCIE-Datacom V1.0 Training Material (IS-IS Basics and Levels)​.
​ Conclusion: The LSP ID in IS-IS consists of System ID, Pseudonode ID, and LSP Number. These
components uniquely identify each LSP within the IS-IS domain.