View Full Huawei H12-831 Exam Dumps and Practice Test Dumps

 

Question 81.

Which OSPF mechanism is used to authenticate routing exchanges between neighboring routers? 

1. OSPF authentication configured consistently on participating interfaces or areas
2. BGP Route Targets
3. MPLS labels
4. STP bridge priorities

Correct Answer: 1. OSPF authentication configured consistently on participating interfaces or areas

Explanation:

OSPF authentication can be configured so that routers accept protocol packets only from neighbors using the expected authentication method and credentials. This helps prevent unauthorized devices from forming OSPF adjacencies or injecting false routing information. Authentication parameters must be compatible between neighboring routers or adjacency establishment can fail. Administrators should combine routing-protocol authentication with other infrastructure security controls, such as protected management access and filtering. MPLS labels and BGP VPN attributes do not authenticate OSPF routing exchanges.

Question 82.

What happens if two directly connected OSPF routers are configured with different Area IDs on the shared link?

1. They automatically select Area 0
2. They normally fail to establish an OSPF adjacency
3. They form an adjacency but ignore LSAs
4. They convert the connection to BGP

Correct Answer: 2. They normally fail to establish an OSPF adjacency

Explanation:

OSPF neighbors on the same link must agree on important parameters, including the Area ID. If one router believes the interface belongs to a different area from the neighboring router, the received Hello packets do not satisfy adjacency requirements. As a result, the routers will normally fail to become OSPF neighbors. Administrators troubleshooting adjacency problems should compare area configuration, authentication, timers, network types, addressing, and other interface-level parameters before investigating unrelated protocols.

Question 83.

Which OSPF network type commonly elects a DR and BDR when several routers share the same Ethernet segment?

1. Point-to-point
2. Loopback
3. Broadcast
4. Point-to-multipoint only

Correct Answer: 3. Broadcast

Explanation:

Ethernet networks typically operate as OSPF broadcast network types. Because several routers may share the same Layer 2 segment, OSPF elects a Designated Router and Backup Designated Router to reduce adjacency and LSA exchange complexity. Routers on a point-to-point connection do not require DR and BDR election because only two OSPF devices participate on the link. Correctly identifying the network type is important because it affects neighbor discovery, election behavior, and adjacency formation.

Question 84.

What is a major purpose of an OSPF totally stubby-style design where supported?

1. Increase external LSA propagation
2. Replace Area 0
3. Convert all OSPF routes to BGP
4. Minimize detailed external and inter-area routing information inside a remote area**

Correct Answer: 4. Minimize detailed external and inter-area routing information inside a remote area

Explanation:

A highly restricted stub-style area can reduce the amount of routing information maintained by routers in a remote location. Instead of carrying large numbers of external and inter-area prefixes, routers can rely primarily on local intra-area information and a default route toward the ABR. This reduces routing-table and link-state database requirements. Such an approach is useful for simple branch areas but must match the platform’s supported OSPF area types and the site’s routing requirements.

Question 85.

Which BGP attribute can an administrator modify to influence outbound path selection within the local autonomous system?

1. Local Preference
2. Ethernet priority
3. OSPF cost only
4. STP path cost

Correct Answer: 1. Local Preference

Explanation:

Local Preference is distributed within an autonomous system and is commonly used to determine which external route internal BGP routers should prefer. A higher Local Preference is generally favored. For example, an organization with two internet providers can assign a higher Local Preference to routes learned from the preferred provider. This directs outbound traffic toward that exit when other higher-priority BGP decision factors are equal. Local Preference is therefore a central BGP traffic-engineering tool.

Question 86.

A BGP administrator wants to influence inbound traffic by making one advertised route less attractive to external autonomous systems. Which technique can be used?

1. Increase OSPF interface cost
2. AS_Path prepending
3. Change the STP root bridge
4. Enable DHCP relay

Correct Answer: 2. AS_Path prepending

Explanation:

AS_Path prepending adds repeated occurrences of the local AS number to selected BGP route advertisements. Since external BGP routers generally prefer shorter AS paths when earlier criteria are equal, the prepended route can become less attractive than another available path. This is a common method of influencing inbound traffic, although neighboring autonomous systems may apply policies that override the expected behavior. It should therefore be used as one part of a broader BGP traffic-engineering strategy.

Question 87.

What is the purpose of the BGP Origin attribute?

1. Identify the physical interface used by the route
2. Specify the destination VLAN
3. Indicate how the route originally entered BGP
4. Encrypt BGP advertisements

Correct Answer: 3. Indicate how the route originally entered BGP

Explanation:

The BGP Origin attribute identifies the general source by which a route entered BGP. It is one of the attributes considered during path selection after several more influential criteria. Different Origin values reflect whether the route was introduced through an interior routing process, an exterior mechanism, or another method. Although Origin can influence route selection, administrators more commonly manipulate attributes such as Local Preference, MED, communities, or AS_Path for traffic engineering.

Question 88.

Why is a loopback interface commonly used as the source of an iBGP session?

1. It automatically encrypts BGP
2. It replaces the IGP
3. It removes the need for IP addressing
4. It provides a stable logical endpoint that is not tied to a single physical interface**

Correct Answer: 4. It provides a stable logical endpoint that is not tied to a single physical interface

Explanation:

A loopback interface remains operational as long as the router itself is functioning, making it more stable than a physical link address. When iBGP sessions use loopback addresses, the session can remain reachable through an alternate physical path if the underlying routing system provides connectivity. This supports resilience in networks with redundant links. The IGP must still provide reachability between the loopback addresses, and appropriate BGP source settings must be configured on both peers.

Question 89.

In IS-IS, which level is primarily responsible for routing between different IS-IS areas?

1. Level 2
2. Level 0
3. Level 1 only
4. DIS level

Correct Answer: 1. Level 2

Explanation:

Level-2 IS-IS provides inter-area routing across the IS-IS domain. Level-1 routers maintain detailed information about destinations inside their own area and normally rely on Level-1-2 routers to reach destinations outside it. Level-1-2 routers participate in both local area routing and the Level-2 backbone. This hierarchical architecture limits topology information and improves scalability. There is no normal IS-IS routing level called Level 0.

Question 90.

What is the purpose of the IS-IS system ID contained in the NET?

1. Determine VLAN membership
2. Uniquely identify the router inside the IS-IS domain
3. Assign an MPLS label
4. Select a BGP Local Preference value

Correct Answer: 2. Uniquely identify the router inside the IS-IS domain

Explanation:

The system ID is a key component of the IS-IS NET and uniquely identifies a router within the IS-IS routing domain. Routers use this identifier when representing topology and building the link-state database. System IDs must be unique to prevent protocol instability and ambiguity. The NET also includes an area address used for Level-1 area membership. The system ID is unrelated to VLAN assignment or BGP path attributes.

Question 91.

What is the primary role of LDP in a traditional MPLS network?

1. Assign IP addresses to hosts
2. Elect the OSPF DR
3. Distribute label bindings between MPLS routers
4. Encrypt VPN traffic

Correct Answer: 3. Distribute label bindings between MPLS routers

Explanation:

Label Distribution Protocol allows MPLS routers to exchange mappings between forwarding equivalence classes and labels. These label bindings help create label-switched forwarding paths through the MPLS network. The underlying IGP normally provides IP reachability, while LDP establishes the label information associated with those routes. LDP does not itself encrypt customer traffic or assign addresses. It is a control-plane protocol that supports MPLS label forwarding.

Question 92.

What is a forwarding equivalence class in MPLS?

1. A list of BGP passwords
2. A VLAN spanning-tree instance
3. A DHCP address pool
4. A group of packets that receive the same MPLS forwarding treatment**

Correct Answer: 4. A group of packets that receive the same MPLS forwarding treatment

Explanation:

A Forwarding Equivalence Class, or FEC, represents packets that are treated equivalently by the MPLS forwarding plane. Packets belonging to the same FEC can be associated with the same label and follow the same forwarding behavior through the MPLS network. The classification may be based on destination reachability or service context. FECs are fundamental to understanding how MPLS separates packet classification from hop-by-hop IP lookups.

Question 93.

In an MPLS Layer 3 VPN, what allows two customers to use the same IPv4 prefix without creating a control-plane conflict?

1. Route Distinguishers
2. STP priorities
3. DHCP options
4. OSPF DR priorities

Correct Answer: 1. Route Distinguishers

Explanation:

A Route Distinguisher is combined with an IPv4 prefix to create a unique VPN route in the provider control plane. Two customers can therefore both use a prefix such as 10.1.1.0/24 while the provider represents them as separate VPN routes. Route Distinguishers make routes unique but do not determine which VPN should import them. Route Targets provide that policy function. Understanding the difference between these two mechanisms is fundamental to MPLS Layer 3 VPN design.

Question 94.

Which MPLS VPN mechanism determines whether a VPN route is imported into a particular VPN instance?

1. Route Distinguisher only
2. Route Target
3. OSPF router ID
4. Ethernet VLAN ID

Correct Answer: 2. Route Target

Explanation:

Route Targets are extended BGP communities that control VPN route import and export policy. A VPN instance exports routes with one or more Route Targets, while another VPN instance imports routes whose Route Targets match its configured policy. This allows flexible VPN topologies such as full mesh, hub-and-spoke, or shared services. Route Distinguishers make overlapping prefixes unique, but Route Targets determine route membership and distribution.

Question 95.

What is the main purpose of VRRP preemption?

1. Disable gateway redundancy
2. Prevent the master from forwarding traffic
3. Allow a higher-priority router to become master when it becomes available
4. Replace dynamic routing

Correct Answer: 3. Allow a higher-priority router to become master when it becomes available

Explanation:

VRRP preemption allows a router with a higher configured priority to take over the master role when it becomes available. This is useful when administrators want a preferred device to handle normal gateway forwarding while another router provides backup service. Without preemption, a lower-priority router that became master during a failure may remain master even after the preferred router recovers. Preemption should be planned carefully so that unstable devices do not cause unnecessary gateway role changes.

Question 96.

Why might an administrator configure a VRRP preemption delay?

1. To disable the virtual IP address
2. To increase BGP AS_Path length
3. To stop all traffic after a recovery
4. To allow a recovering router time to stabilize before reclaiming the master role**

Correct Answer: 4. To allow a recovering router time to stabilize before reclaiming the master role

Explanation:

A preemption delay prevents a recovered higher-priority router from immediately becoming VRRP master. This gives routing protocols, interfaces, and other dependent services time to converge and stabilize before the router begins forwarding gateway traffic again. Without a delay, a router may reclaim the master role before its upstream routing is fully ready, potentially creating temporary packet loss. Preemption delay therefore improves the operational stability of first-hop redundancy.

Question 97.

What is the purpose of link aggregation in a campus or data center network?

1. Combine physical links for increased bandwidth and redundancy
2. Replace all routing protocols
3. Disable Layer 2 redundancy
4. Assign public IP addresses automatically

Correct Answer: 1. Combine physical links for increased bandwidth and redundancy

Explanation:

Link aggregation combines multiple physical Ethernet links into a single logical connection. This can increase total available bandwidth and provide resilience if one member link fails. Traffic is normally distributed across members according to a hashing algorithm rather than every packet being sent over all links simultaneously. Huawei devices commonly implement this using Eth-Trunk interfaces, with LACP often used to negotiate and monitor participating links. Link aggregation is widely used between switches, routers, and servers.

Question 98.

What is a major advantage of using LACP instead of a purely static Eth-Trunk?

1. LACP replaces IP routing
2. LACP can negotiate and monitor participating member links
3. LACP creates BGP routes automatically
4. LACP provides packet encryption

Correct Answer: 2. LACP can negotiate and monitor participating member links

Explanation:

LACP enables devices on both ends of a link aggregation to exchange control information about potential members. This helps determine which interfaces can actively participate and provides better visibility into member status than a purely static configuration. If a link becomes unsuitable, LACP can adjust the active membership according to the configured aggregation behavior. It does not replace routing, encryption, or BGP. Its purpose is to improve the operation and manageability of aggregated Ethernet links.

Question 99.

A network requires very fast convergence after a routed link failure. Which technology can complement OSPF, IS-IS, or BGP for faster failure detection?

1. BFD
2. DHCP relay
3. STP PortFast
4. Route Distinguisher

Correct Answer: 1. BFD

Explanation:

Bidirectional Forwarding Detection provides rapid liveness detection between network devices and can be associated with dynamic routing protocols. When BFD detects that a forwarding path has failed, the routing protocol can react more quickly than it might using its normal Hello or keepalive timers. This is valuable for applications with strict convergence requirements. BFD does not calculate routes itself; OSPF, IS-IS, or BGP still determines the alternate path after receiving failure information.

Question 100.

Which network design approach BEST supports scalability, resilience, and predictable routing in a large Huawei-based network?

1. Use one flat broadcast domain and advertise every route everywhere
2. Disable routing redundancy to simplify the topology
3. Redistribute all protocols without filtering
4. Use hierarchical routing, summarization, controlled policies, redundant paths, fast failure detection, and structured addressing**

Correct Answer: 4. Use hierarchical routing, summarization, controlled policies, redundant paths, fast failure detection, and structured addressing

Explanation:

Large networks benefit from deliberate hierarchy and clear protocol boundaries. Structured addressing enables summarization, reducing routing-table size and limiting propagation of topology changes. Route policies prevent unwanted advertisements and make traffic engineering predictable. Redundant links and gateway mechanisms improve availability, while BFD can accelerate failure detection. MPLS, BGP, OSPF, IS-IS, multicast, and QoS should each be deployed according to defined design objectives rather than combined without policy. This approach produces a network that is easier to scale, troubleshoot, and operate reliably.