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

 

Question 321.

In OSPF, which mechanism helps reduce the number of adjacencies required on a broadcast multi-access network?

1. DR and BDR election
2. Route reflection
3. MPLS label distribution
4. BGP communities

Correct Answer: 1. DR and BDR election

Explanation:

OSPF uses a Designated Router and Backup Designated Router on broadcast multi-access networks to reduce the number of full adjacencies and simplify LSA exchange. Instead of every router forming a full adjacency with every other router, most devices form full adjacencies primarily with the DR and BDR. This greatly reduces control-plane complexity as the number of routers on the segment increases. Route reflection is a BGP scaling feature, while MPLS labels and communities serve unrelated purposes.

Question 322.

What is the main advantage of using OSPF areas in a large enterprise network?

1. They eliminate the need for routing tables
2. They limit the scope of detailed topology information and SPF recalculations
3. They automatically encrypt routing traffic
4. They remove the need for redundant links

Correct Answer: 2. They limit the scope of detailed topology information and SPF recalculations

Explanation:

OSPF areas create hierarchical boundaries that help contain topology information. Routers within one area maintain detailed knowledge of that area’s topology, while other areas generally receive summarized inter-area reachability rather than every internal link-state detail. This reduces LSDB size and limits the impact of certain topology changes. Proper area design improves scalability, especially in large networks with many routers and links. Areas do not eliminate routing tables or provide encryption by themselves.

Question 323.

Which OSPF route type is generally preferred over an external OSPF route when both reach the same prefix?

1. External Type 2 only
2. External Type 1 only
3. An internal OSPF route such as intra-area or inter-area
4. A BGP route regardless of preference

Correct Answer: 3. An internal OSPF route such as intra-area or inter-area

Explanation:

Within OSPF’s route-selection hierarchy, internal OSPF routes are generally preferred over external routes. An intra-area route is normally preferred over an inter-area route, and both are preferred over externally redistributed paths. This behavior helps keep traffic on native OSPF paths when the same destination is also being redistributed from another routing source. Administrators should understand this hierarchy when designing redistribution and backup-route strategies to avoid unexpected forwarding behavior.

Question 324.

What is a key risk of redistributing routes between two routing protocols in both directions without proper filtering?

1. Ethernet frame size increases
2. MPLS labels expire immediately
3. VRRP stops functioning
4. Routing loops or repeated route feedback can occur**

Correct Answer: 4. Routing loops or repeated route feedback can occur

Explanation:

Bidirectional redistribution can cause a route learned from one protocol to be injected into another and then redistributed back into the original protocol. Without route tagging, filtering, or carefully designed policy, this can create feedback loops, incorrect route preference, or unstable routing behavior. Administrators commonly use route policies and tags to identify redistributed routes and prevent them from being reintroduced improperly. Redistribution should therefore be treated as a controlled routing boundary rather than a simple route-copying mechanism.

Question 325.

Which BGP mechanism is BEST suited to applying the same policy to many related prefixes?

1. Community tagging
2. Router ID changes
3. Hold timer adjustment
4. TCP window scaling

Correct Answer: 1. Community tagging

Explanation:

BGP communities allow administrators to group related routes logically and then apply common routing policy based on those tags. This is more scalable than writing separate policy statements for every prefix. For example, routes can be tagged according to customer, region, traffic-engineering requirement, or export policy. A route policy can then modify Local Preference, control advertisement, or take other actions based on the community. Communities are therefore an important tool in structured BGP policy design.

Question 326.

Which BGP attribute can be modified to make one route less attractive by increasing the number of apparent autonomous systems in the path?

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

Correct Answer: 2. AS_Path

Explanation:

AS_Path prepending deliberately adds repeated instances of the local AS number to a route advertisement. Because BGP commonly prefers shorter AS paths when more influential decision criteria are equal, the prepended route may become less attractive to external networks. This technique is often used to influence inbound traffic across multiple links. However, remote networks may apply policies such as higher Local Preference that override the effect of AS_Path length.

Question 327.

Why is route summarization useful in BGP?

1. It increases the number of advertised prefixes
2. It prevents all backup paths
3. It can reduce routing-table size and the number of routing updates
4. It replaces route filtering

Correct Answer: 3. It can reduce routing-table size and the number of routing updates

Explanation:

BGP summarization, or aggregation, combines multiple more-specific prefixes into a broader advertisement where addressing and policy allow. This can reduce the number of routes carried throughout a network and limit the propagation of changes affecting individual more-specific prefixes. Aggregation can improve scalability, but administrators must ensure that the summarized route represents reachable destinations correctly. Summary routes should therefore be planned together with address structure and failure behavior.

Question 328.

What is the main purpose of BGP authentication between peers?

1. Assign routing metrics automatically
2. Create an MPLS VPN
3. Replace prefix filtering
4. Help protect the peering session from unauthorized establishment or spoofed session attempts**

Correct Answer: 4. Help protect the peering session from unauthorized establishment or spoofed session attempts

Explanation:

BGP session authentication can help ensure that peer relationships are established only between routers using the expected credentials. This adds protection against unauthorized or accidental session establishment. Authentication should be combined with prefix filtering, infrastructure access controls, and other routing-security practices because it does not validate whether advertised routes are authorized. It protects the peering relationship itself rather than replacing routing policy or route-origin controls.

Question 329.

In IS-IS, which router type participates only in routing within a single local area?

1. Level-1 router
2. Level-2 router
3. Level-1-2 router
4. DIS only

Correct Answer: 1. Level-1 router

Explanation:

A Level-1 IS-IS router maintains detailed topology information for its own area and forms Level-1 adjacencies with other eligible routers in that area. For destinations outside the local area, it typically relies on a Level-1-2 router that provides access toward the Level-2 backbone. This hierarchical design allows local routers to avoid maintaining full inter-area topology knowledge. Level-2 routers handle backbone routing, while Level-1-2 routers connect the two routing levels.

Question 330.

What is the primary purpose of route leaking between IS-IS levels when configured?

1. Disable inter-area connectivity
2. Make selected routes from one routing level available in another level
3. Replace the system ID
4. Elect the DIS

Correct Answer: 2. Make selected routes from one routing level available in another level

Explanation:

IS-IS route leaking can selectively advertise routing information between Level-1 and Level-2 domains when a design requires more specific reachability than the normal hierarchy provides. For example, selected Level-2 routes may be leaked into Level-1 to improve path selection. Because excessive leaking can reduce the scalability benefits of hierarchy, it should be implemented carefully and only where needed. Routing policy can control which routes are leaked.

Question 331.

What is the primary function of an MPLS label stack entry?

1. Carry forwarding information used by MPLS routers
2. Encrypt the IP packet
3. Assign a VLAN to the source host
4. Replace the destination IP address

Correct Answer: 1. Carry forwarding information used by MPLS routers

Explanation:

An MPLS label stack entry contains label information that routers use to make forwarding decisions. Depending on the service, one packet may carry several labels, such as an outer transport label and an inner VPN label. MPLS routers perform push, swap, and pop operations as the packet travels through the network. Labels do not encrypt the packet or replace the IP addressing scheme; instead, they provide an additional forwarding mechanism above the underlying link layer.

Question 332.

Which MPLS function allows a core router to forward a packet without examining the full customer IP routing context?

1. VRRP preemption
2. Label switching
3. OSPF summarization
4. DHCP relay

Correct Answer: 2. Label switching

Explanation:

MPLS core routers can forward packets by examining the top label and consulting their label forwarding tables. This means a core P router does not need to maintain every customer’s VPN routing information. Instead, the label directs the packet along the appropriate provider transport path. This separation between customer routing at the PE layer and label forwarding in the core contributes significantly to MPLS scalability.

Question 333.

What is the main role of an MP-BGP Route Target in an MPLS Layer 3 VPN?

1. Determine physical interface speed
2. Set VRRP master priority
3. Control which VPN instances import or export particular routes
4. Select the OSPF DR

Correct Answer: 3. Control which VPN instances import or export particular routes

Explanation:

Route Targets are extended BGP communities used to define VPN route membership. When a PE exports a VPN route, it attaches one or more Route Targets. Other VPN instances import that route only if their configured policy matches the relevant Route Target. This enables flexible VPN connectivity models, including full-mesh, hub-and-spoke, and shared services. Route Targets therefore control distribution policy, while Route Distinguishers provide prefix uniqueness.

Question 334.

Which statement BEST describes penultimate hop popping in MPLS?

1. The ingress PE removes all labels
2. The CE removes the VPN label
3. The first P router removes the IP header
4. The router before the egress LSR removes the outer transport label when appropriate**

Correct Answer: 4. The router before the egress LSR removes the outer transport label when appropriate

Explanation:

Penultimate hop popping allows the router immediately before the egress LSR to remove the outer MPLS transport label. This can reduce the amount of label processing required at the egress. If the packet carries an additional service or VPN label, that inner label can remain for the egress PE to process. PHP is therefore an optimization in MPLS forwarding and does not imply that every label is removed before the packet reaches the egress device.

Question 335.

Which VRRP parameter is generally preferred when selecting the master router?

1. Higher effective priority
2. Lower OSPF cost
3. Higher MPLS label value
4. Lower Ethernet MTU

Correct Answer: 1. Higher effective priority

Explanation:

VRRP master selection is primarily based on priority. The eligible router with the higher effective VRRP priority is generally preferred to act as master. Tracking can reduce a router’s effective priority when an important uplink or route fails, allowing a healthier backup to take over. Preemption can later allow a recovered higher-priority router to regain mastership. These mechanisms provide predictable first-hop gateway redundancy.

Question 336.

What is the main purpose of a VRRP preemption delay?

1. Prevent the backup from ever becoming master
2. Allow a recovering preferred router time to restore routing before taking over
3. Increase the number of virtual IP addresses
4. Change OSPF area membership

Correct Answer: 2. Allow a recovering preferred router time to restore routing before taking over

Explanation:

A recovering router may restore its LAN-facing interface before its routing protocols or upstream links are fully operational. If it immediately preempts the current VRRP master, hosts could begin forwarding through a gateway that does not yet have complete reachability. A preemption delay allows time for the device to stabilize before assuming mastership. This improves reliability during recovery and reduces unnecessary traffic interruption.

Question 337.

Which statement BEST describes LACP standby links in an Eth-Trunk?

1. They can replace failed active members when required
2. They are permanently disabled and never used
3. They advertise BGP routes
4. They provide OSPF summarization

Correct Answer: 1. They can replace failed active members when required

Explanation:

In an LACP aggregation, some candidate links can remain in standby when the configured number of active members has already been reached. If an active member fails, an eligible standby interface can become active according to the LACP selection process. This provides additional redundancy while keeping the active bundle within configured limits. Standby links are part of link-aggregation behavior and are unrelated to Layer 3 routing.

Question 338.

Which QoS mechanism is used to identify traffic based on fields such as source address, destination address, protocol, or DSCP value?

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

Correct Answer: 2. Traffic classification

Explanation:

Traffic classification examines packet fields and determines which QoS class a packet belongs to. Matching can be based on IP addresses, transport protocols, port numbers, VLAN information, DSCP values, or other supported criteria. Once a packet is classified, the network can apply actions such as marking, policing, shaping, scheduling, or congestion avoidance. Accurate classification is therefore the foundation of effective QoS policy.

Question 339.

What is the primary purpose of Weighted Random Early Detection or a similar congestion-avoidance mechanism?

1. Drop selected packets before queues become completely full to reduce severe congestion
2. Establish BGP sessions faster
3. Create MPLS VPNs
4. Elect a VRRP master

Correct Answer: 1. Drop selected packets before queues become completely full to reduce severe congestion

Explanation:

Congestion-avoidance mechanisms such as WRED begin selectively dropping traffic before a queue reaches complete saturation. The intention is to signal responsive transport protocols to reduce their sending rates and prevent widespread tail drops. Different traffic classes or markings can receive different drop thresholds. WRED complements queue scheduling and shaping but does not replace classification or bandwidth planning. It is designed to improve behavior during developing congestion.

Question 340.

Which architecture BEST supports a resilient and scalable Huawei network with advanced routing, MPLS, redundancy, and QoS?

1. Use one routing domain with unrestricted redistribution everywhere
2. Depend on a single physical path for critical traffic
3. Avoid route filtering and summarization
4. Use hierarchical routing, controlled policies, summarization, redundant links, rapid failure detection, gateway redundancy, and consistent QoS design**

Correct Answer: 4. Use hierarchical routing, controlled policies, summarization, redundant links, rapid failure detection, gateway redundancy, and consistent QoS design

Explanation:

Scalable networks require clear separation of responsibilities. Hierarchical routing limits the scope of topology changes, while route filtering and summarization reduce unnecessary routing information. Redundant links and devices improve availability, and technologies such as BFD and VRRP accelerate recovery from failures. MPLS can provide scalable service transport, while QoS ensures predictable treatment of important applications during congestion. Consistent policy and monitoring help keep these technologies working together without creating unnecessary operational complexity.