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

 

Question 181.

In OSPF, what is the primary purpose of the backbone area?

1. Provide the central path for inter-area routing
2. Assign IP addresses to routers
3. Create MPLS labels
4. Replace all non-backbone areas

Correct Answer: 1. Provide the central path for inter-area routing

Explanation:

Area 0 serves as the OSPF backbone and is central to the hierarchical design of OSPF. Non-backbone areas normally connect to Area 0 through Area Border Routers so inter-area routing information can be exchanged in a structured way. This design limits the amount of topology information every router must maintain and helps improve scalability. The backbone does not assign addresses or replace every other area. Its main function is to connect areas and provide the logical core through which inter-area reachability is maintained.

Question 182.

Which OSPF router type introduces routes learned from another routing protocol into the OSPF domain?

1. Internal router
2. Autonomous System Boundary Router
3. Designated Router
4. Backup Designated Router

Correct Answer: 2. Autonomous System Boundary Router

Explanation:

An ASBR redistributes routes from another routing source into OSPF. Those routes may originate from BGP, static routing, IS-IS, or another protocol. In normal OSPF areas, the ASBR typically advertises external destinations using Type 5 LSAs. In an NSSA, external information is initially represented differently. An internal router keeps all OSPF interfaces in the same area, while DR and BDR roles are related to multi-access network adjacency management rather than route redistribution.

Question 183.

Why is OSPF route summarization useful in a multi-area network?

1. It disables all detailed routes
2. It increases the number of LSAs
3. It can reduce routing-table size and limit propagation of detailed topology changes
4. It converts OSPF into BGP

Correct Answer: 3. It can reduce routing-table size and limit propagation of detailed topology changes

Explanation:

Summarization allows multiple related prefixes to be represented by a broader route when advertised between routing regions. This can reduce the number of routing entries that other areas must process and can help isolate detailed changes within one part of the network. Effective summarization depends on structured IP addressing because scattered prefixes are difficult to aggregate cleanly. Summarization improves scalability, but administrators must ensure that an aggregate does not incorrectly attract traffic toward destinations that are no longer reachable.

Question 184.

What is the purpose of the OSPF Hello protocol on a broadcast network?

1. Distribute MPLS labels
2. Advertise BGP communities
3. Provide DHCP leases
4. Discover neighbors, maintain relationships, and participate in DR/BDR election**

Correct Answer: 4. Discover neighbors, maintain relationships, and participate in DR/BDR election

Explanation:

OSPF Hello packets are fundamental to neighbor discovery and adjacency maintenance. Routers send Hellos periodically and use the received information to determine whether neighboring OSPF devices are reachable and have compatible parameters. On broadcast networks, Hello packets also carry information used during the Designated Router and Backup Designated Router election process. If Hellos stop arriving for the configured Dead interval, the neighbor can be declared down. Hello processing therefore supports both topology formation and failure detection.

Question 185.

Which BGP attribute is generally preferred when it has the shortest value in terms of autonomous systems traversed?

1. AS_Path
2. Local Preference
3. MED
4. Community

Correct Answer: 1. AS_Path

Explanation:

The AS_Path attribute records the autonomous systems that a route has crossed. During BGP best-path selection, a shorter AS_Path is generally preferred when more influential criteria are equal. AS_Path also provides an important loop-prevention function because a router normally rejects a route if its own AS number already appears in the path. Local Preference and MED use numerical values with different comparison rules, while communities are primarily policy tags rather than a direct path-length measurement.

Question 186.

A company wants one ISP to be the preferred outbound path and another ISP to act mainly as backup. Which BGP attribute is most appropriate to manipulate internally?

1. Origin
2. Local Preference
3. Router ID
4. Cluster List

Correct Answer: 2. Local Preference

Explanation:

Local Preference is one of the most direct tools for controlling outbound BGP routing inside an autonomous system. Routes learned through the preferred ISP can be assigned a higher Local Preference than routes learned through the backup provider. Internal BGP routers then generally choose the route with the higher value. This attribute is distributed inside the AS and does not need to be advertised to external neighbors. Other BGP attributes can influence routing, but Local Preference is especially suited to selecting preferred exit points.

Question 187.

Which BGP attribute can be used to indicate a preferred inbound entry point to a neighboring autonomous system?

1. Local Preference
2. Weight
3. MED
4. OSPF cost

Correct Answer: 3. MED

Explanation:

The Multi-Exit Discriminator is designed to suggest which connection a neighboring autonomous system should prefer when sending traffic into the advertising AS. Lower MED values are normally preferred when compared. MED is most predictable when multiple paths are learned from the same neighboring AS, though implementation and policy can affect how it is evaluated. It is advisory rather than mandatory because the receiving network can override the suggestion through its own BGP policy.

Question 188.

Why are prefix filters important on an eBGP connection?

1. They provide link aggregation
2. They assign MPLS labels
3. They determine VRRP mastership
4. They help prevent unauthorized or unintended route advertisements**

Correct Answer: 4. They help prevent unauthorized or unintended route advertisements

Explanation:

Prefix filtering is a key BGP routing-security practice. It allows administrators to define which networks may be accepted from or advertised to an external peer. Without filtering, accidental redistribution or configuration errors can cause route leaks that affect local or remote networks. Prefix lists and route policies can be used to implement precise controls. External BGP sessions should be treated as routing-policy boundaries where both inbound and outbound advertisements are validated carefully.

Question 189.

What is the main role of the DIS on an IS-IS broadcast network?

1. Represent the multi-access network and assist with link-state database synchronization
2. Act as the default gateway for all hosts
3. Replace Level-2 routing
4. Assign IPv6 addresses

Correct Answer: 1. Represent the multi-access network and assist with link-state database synchronization

Explanation:

On an IS-IS broadcast network, a Designated Intermediate System is elected to help represent the shared segment efficiently in the link-state topology and support database synchronization. This reduces complexity in a network where multiple routers share the same media. The DIS concept differs from OSPF DR/BDR behavior, including election and failover details. It does not act as the host default gateway or replace the Level-2 backbone function.

Question 190.

What is the purpose of an IS-IS Level-1-2 router?

1. Operate only within one Level-1 area
2. Participate in both intra-area Level-1 routing and inter-area Level-2 routing
3. Replace every other IS-IS router
4. Provide only Layer 2 switching

Correct Answer: 2. Participate in both intra-area Level-1 routing and inter-area Level-2 routing

Explanation:

A Level-1-2 router participates in both routing levels of IS-IS. It maintains detailed topology information for its local Level-1 area while also joining the Level-2 backbone used for inter-area reachability. This allows Level-1 routers to reach destinations outside their own areas through Level-1-2 devices. The hierarchical design limits the amount of information that local routers need to maintain and supports greater routing scalability.

Question 191.

In MPLS, what is the purpose of an ingress Label Edge Router?

1. Classify incoming packets and push appropriate MPLS labels
2. Remove every MPLS label from all packets
3. Perform only Layer 2 switching
4. Disable IP routing

Correct Answer: 1. Classify incoming packets and push appropriate MPLS labels

Explanation:

At the entry to an MPLS domain, the ingress Label Edge Router classifies traffic into a Forwarding Equivalence Class and applies the appropriate MPLS label or label stack. Once labeled, the packet can be forwarded through the MPLS core using label operations. Transit routers commonly swap labels, while labels are eventually removed near or at the egress. The ingress LER therefore provides the transition between ordinary incoming traffic and MPLS label-based forwarding.

Question 192.

What is the main function of an MPLS transit LSR?

1. Maintain customer VRFs for every VPN
2. Swap incoming labels for outgoing labels and forward packets
3. Assign host IP addresses
4. Create BGP communities

Correct Answer: 2. Swap incoming labels for outgoing labels and forward packets

Explanation:

A transit Label Switching Router forwards MPLS traffic based on label information. It typically receives a packet with one label, looks up the required forwarding action, replaces the incoming label with another label, and forwards the packet to the next hop. This label-swap behavior is a core part of MPLS forwarding. Transit core routers can therefore move traffic efficiently without maintaining all customer VPN routes, depending on the service design.

Question 193.

Which MPLS Layer 3 VPN mechanism makes overlapping customer prefixes unique in the provider control plane?

1. Route Target
2. VRRP priority
3. Route Distinguisher
4. LACP priority

Correct Answer: 3. Route Distinguisher

Explanation:

A Route Distinguisher is combined with an IPv4 prefix to create a unique VPN route. This allows two or more customers to use identical private address ranges without creating ambiguity in the provider’s MP-BGP control plane. Route Distinguishers do not control which VPN imports a route. That function is handled through Route Targets. Distinguishing these two concepts is essential when designing or troubleshooting MPLS Layer 3 VPN services.

Question 194.

Which mechanism controls the import and export of VPN routes in an MPLS Layer 3 VPN?

1. OSPF router ID
2. MPLS EXP value only
3. Ethernet VLAN ID
4. Route Target**

Correct Answer: 4. Route Target

Explanation:

Route Targets are extended BGP communities used to control VPN route distribution. When a VPN instance exports a route, it can attach one or more Route Targets. Other VPN instances import routes based on configured matching Route Targets. This enables flexible topologies, including full-mesh, hub-and-spoke, and shared-service VPN designs. Route Distinguishers provide uniqueness, while Route Targets provide membership and routing-policy control.

Question 195.

What is the primary purpose of VRRP?

1. Provide first-hop default-gateway redundancy
2. Create BGP route reflectors
3. Distribute MPLS labels
4. Prevent Layer 2 loops

Correct Answer: 1. Provide first-hop default-gateway redundancy

Explanation:

VRRP allows multiple routers to share a virtual IP address that hosts use as their default gateway. One router acts as master and forwards traffic, while one or more backup routers can take over if the master fails. This prevents hosts from needing to change their configured gateway during a router failure. Features such as preemption and tracking can refine failover behavior. VRRP provides first-hop redundancy rather than dynamic routing or Layer 2 loop prevention.

Question 196.

Why can VRRP interface or route tracking improve availability?

1. It increases the virtual IP address size
2. It allows mastership to reflect upstream path health rather than only the local LAN interface
3. It creates a BGP AS_Path
4. It disables failover

Correct Answer: 2. It allows mastership to reflect upstream path health rather than only the local LAN interface

Explanation:

A VRRP master can remain reachable on the local LAN even when its important upstream connection has failed. Without tracking, hosts may continue sending traffic to a gateway that cannot reach remote destinations. Tracking an uplink or route can reduce the device’s effective VRRP priority when that resource fails, allowing a healthier backup to become master. This provides more meaningful redundancy because the gateway role follows end-to-end connectivity rather than only local interface status.

Question 197.

What is the main purpose of LACP in an Eth-Trunk?

1. Negotiate and monitor aggregated member links
2. Assign MPLS Route Targets
3. Replace all dynamic routing
4. Create DHCP pools

Correct Answer: 1. Negotiate and monitor aggregated member links

Explanation:

LACP provides a standards-based mechanism for devices to exchange information about interfaces participating in a link aggregation. It helps determine which links are suitable to become active members and provides better operational visibility than a purely static aggregation. If a member becomes unavailable or inconsistent, LACP can adjust the active bundle according to the configuration. It complements Eth-Trunk functionality by improving negotiation and monitoring rather than providing Layer 3 routing.

Question 198.

Which QoS mechanism is used to delay excess traffic so it can be transmitted later at a controlled rate?

1. Traffic policing
2. Traffic shaping
3. Route summarization
4. BFD

Correct Answer: 2. Traffic shaping

Explanation:

Traffic shaping uses buffering to smooth bursts and regulate the output rate. When traffic temporarily exceeds the configured rate, packets can be queued and transmitted later as bandwidth becomes available. This differs from policing, which commonly drops or remarks traffic that exceeds the permitted profile. Shaping is useful when temporary delay is acceptable and packet loss should be reduced. Because buffering introduces latency, it must be designed according to application requirements and available memory.

Question 199.

What is the primary benefit of using BFD with OSPF, IS-IS, or BGP?

1. Faster detection of forwarding-path failures
2. Automatic route summarization
3. MPLS VPN creation
4. VLAN assignment

Correct Answer: 1. Faster detection of forwarding-path failures

Explanation:

BFD provides rapid liveness detection between network devices and can be associated with dynamic routing protocols. When the forwarding path fails, BFD can detect the condition more quickly than normal routing-protocol Hello or keepalive timers in many designs. The routing protocol can then react and calculate or select an alternate path. BFD does not exchange routing information itself; it complements OSPF, IS-IS, or BGP by accelerating failure detection and supporting faster convergence.

Question 200.

Which architecture BEST supports scalability and predictable operation in a large Huawei routed network?

1. One large broadcast domain with uncontrolled route redistribution
2. Disable route filtering to simplify configuration
3. Use only static routes regardless of scale
4. Use hierarchical topology, structured addressing, summarization, controlled routing policy, redundancy, and fast failure detection**

Correct Answer: 4. Use hierarchical topology, structured addressing, summarization, controlled routing policy, redundancy, and fast failure detection

Explanation:

Large networks benefit from clearly structured routing domains and consistent policy. Hierarchical topology reduces the scope of failures, while structured addressing allows effective route summarization. Filtering and route policies prevent unintended advertisements and control traffic engineering. Redundant devices and links improve availability, and BFD can speed failure detection where required. Technologies such as OSPF, IS-IS, BGP, MPLS, VRRP, and QoS should each have defined roles so interactions remain predictable and troubleshooting remains manageable.