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

 

Question 361.

In OSPF, what is the purpose of route tagging during redistribution?

1. Identify redistributed routes so policies can prevent unwanted route feedback
2. Increase interface bandwidth
3. Elect the DR
4. Create MPLS labels

Correct Answer: 1. Identify redistributed routes so policies can prevent unwanted route feedback

Explanation:

Route tags can mark routes when they are redistributed from one routing protocol into another. A later policy can match the tag and prevent those routes from being redistributed back into the original protocol, which helps reduce the risk of routing loops or route feedback. Tags can also classify routes according to source or policy. They do not change physical bandwidth or perform OSPF neighbor election. Careful tagging is especially useful in networks where redistribution occurs at multiple points.

Question 362.

What is a likely consequence of configuring different OSPF Hello intervals on two directly connected routers?

1. They automatically negotiate a common timer
2. They may fail to establish an OSPF adjacency
3. They form an adjacency but use BGP timers instead
4. They automatically become DR and BDR

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

Explanation:

OSPF neighbors must use compatible Hello and Dead timer values on a shared link. If the Hello intervals differ, the routers will generally reject one another as valid OSPF neighbors and fail to establish the expected adjacency. Timer mismatches are therefore a common troubleshooting point when IP connectivity exists but OSPF does not reach the Full state. Authentication, area assignment, subnet parameters, and network type should also be checked during adjacency troubleshooting.

Question 363.

Why is OSPF area design important in a large network?

1. It removes the need for IP addressing
2. It guarantees all links have equal cost
3. It can contain topology changes and reduce the size of link-state databases
4. It eliminates the need for route policies

Correct Answer: 3. It can contain topology changes and reduce the size of link-state databases

Explanation:

Dividing a large OSPF domain into areas limits the amount of detailed topology information each router must maintain. Changes inside one area do not necessarily require every router in other areas to process the same detailed LSAs or rerun SPF for that internal topology. This improves scalability and fault containment. Area design also creates natural locations for route summarization. Poor area design can increase operational complexity, so hierarchy should reflect network structure and expected traffic paths.

Question 364.

What is a major operational advantage of summarizing OSPF routes at an ABR?

1. It increases the number of route entries
2. It disables inter-area routing
3. It changes OSPF into a distance-vector protocol
4. It can hide detailed prefix changes from other areas**

Correct Answer: 4. It can hide detailed prefix changes from other areas

Explanation:

When several related prefixes are summarized into a broader route, routers in other areas do not need to know about every individual component prefix. A failure affecting one more-specific route may therefore remain contained within the originating area while the summary remains valid. This reduces routing-table size and limits control-plane churn. Effective summarization requires a structured addressing plan so the aggregate accurately represents the reachable destinations behind the ABR.

Question 365.

Which BGP attribute is commonly manipulated to influence outbound traffic from the local AS?

1. Local Preference
2. Originator_ID
3. Cluster_List
4. Hold Time

Correct Answer: 1. Local Preference

Explanation:

Local Preference is distributed within the local autonomous system and is commonly used to determine which external path internal BGP routers should prefer. A higher Local Preference is generally more attractive. Administrators can therefore assign a higher value to routes learned from a preferred upstream provider. This provides a direct way to influence outbound traffic. Originator_ID and Cluster_List are mainly associated with route reflection, while Hold Time is a session-liveness parameter.

Question 366.

Which BGP technique is commonly used to make a route advertisement appear less attractive to external networks?

1. Decrease Local Preference inside the remote AS
2. AS_Path prepending
3. Increase VRRP priority
4. Change the OSPF area number

Correct Answer: 2. AS_Path prepending

Explanation:

AS_Path prepending adds repeated copies of the local autonomous system number to a route advertisement. Since BGP often prefers shorter AS paths when higher-priority decision factors are equal, the modified route may appear less attractive to external networks. This technique is often used to influence inbound traffic across multiple external links. It is not guaranteed, however, because remote networks can apply their own policies that override AS_Path length.

Question 367.

What is the main benefit of BGP route reflection?

1. It removes the need for eBGP
2. It replaces the IGP
3. It improves iBGP scalability by reducing full-mesh requirements
4. It creates MPLS labels

Correct Answer: 3. It improves iBGP scalability by reducing full-mesh requirements

Explanation:

Traditional iBGP requires a full mesh of sessions because routes learned from one iBGP peer are not normally advertised to another. Route reflectors relax this requirement by reflecting routes between selected clients and peers. This reduces the number of BGP sessions needed in large autonomous systems. Redundant route reflectors can improve resiliency. The underlying IGP is still required to provide reachability among BGP speakers, so route reflection does not replace internal routing.

Question 368.

Which BGP route-reflector attribute identifies the original iBGP router that originated a reflected route?

1. MED
2. Community
3. Next_Hop
4. Originator_ID**

Correct Answer: 4. Originator_ID

Explanation:

Originator_ID identifies the iBGP router from which a reflected route originally came. A route reflector uses this information as part of the loop-prevention mechanisms associated with route reflection. If a route would be reflected back toward its originator, the information can be used to prevent inappropriate propagation. Cluster_List complements this mechanism by recording reflector clusters the route has traversed. These attributes make route reflection scalable without losing essential loop controls.

Question 369.

In IS-IS, which PDU contains detailed link-state information advertised by a router?

1. Link State PDU
2. Hello PDU only
3. BGP UPDATE
4. MPLS Label Mapping

Correct Answer: 1. Link State PDU

Explanation:

An IS-IS Link State PDU contains topology and reachability information originated by a router. LSPs are flooded throughout the appropriate IS-IS level so routers can build synchronized link-state databases. Those databases are then used by the SPF algorithm to calculate routes. Hello PDUs are primarily used for neighbor discovery and adjacency maintenance rather than carrying the detailed topology information needed for route calculation.

Question 370.

What is the main purpose of the DIS election in an IS-IS broadcast network?

1. Select the default gateway for hosts
2. Improve representation and synchronization of the shared multi-access segment
3. Choose the BGP route reflector
4. Assign MPLS service labels

Correct Answer: 2. Improve representation and synchronization of the shared multi-access segment

Explanation:

On an IS-IS broadcast network, the Designated Intermediate System helps represent the shared LAN as a pseudonode and assists with link-state database synchronization. This simplifies topology representation where multiple IS-IS routers share the same segment. The DIS has a different election and operational model from the OSPF DR/BDR process, but both mechanisms address multi-access routing complexity. The DIS does not function as an end-host default gateway.

Question 371.

What is the purpose of an MPLS Label Switched Path?

1. Provide a path through the MPLS domain based on label forwarding
2. Assign customer IP addresses
3. Elect an OSPF DR
4. Configure VRRP priority

Correct Answer: 1. Provide a path through the MPLS domain based on label forwarding

Explanation:

A Label Switched Path is the forwarding path that labeled packets follow through an MPLS network. Routers along the path use label forwarding entries to determine the required operations, such as swapping or popping labels. LSPs can support transport between provider edge routers and form the foundation for services such as MPLS VPNs. The LSP forwarding process is distinct from host addressing, OSPF election, and first-hop gateway redundancy.

Question 372.

What is the purpose of LDP label mappings?

1. Define customer VLANs
2. Associate forwarding equivalence classes with MPLS labels
3. Change BGP Local Preference
4. Configure VRRP timers

Correct Answer: 2. Associate forwarding equivalence classes with MPLS labels

Explanation:

LDP distributes bindings that associate a forwarding equivalence class with a locally assigned MPLS label. Neighboring MPLS routers use these mappings to build forwarding information for label-switched paths. The underlying IGP supplies reachability, while LDP adds label information that allows MPLS forwarding. This cooperation between routing and label distribution is fundamental to traditional MPLS deployments. LDP mappings do not define VLAN membership or BGP policy.

Question 373.

Which component on a PE router provides routing-table separation between different MPLS VPN customers?

1. Route Distinguisher alone
2. LDP session
3. VPN instance or VRF
4. OSPF DR

Correct Answer: 3. VPN instance or VRF

Explanation:

A VRF, also called a VPN instance, provides a separate routing and forwarding context for a customer or VPN on the PE router. Interfaces associated with one VRF use that VRF’s routing table rather than the global routing table or another customer’s table. This allows overlapping customer addressing while maintaining isolation. Route Distinguishers and Route Targets support MP-BGP route exchange, but the VRF provides the local forwarding separation.

Question 374.

What is the primary function of the outer label in a typical two-label MPLS Layer 3 VPN packet?

1. Identify the customer application
2. Identify the VRRP group
3. Select an OSPF area
4. Carry the packet across the provider core toward the egress PE**

Correct Answer: 4. Carry the packet across the provider core toward the egress PE

Explanation:

The outer MPLS label generally serves as the transport label used to move the packet across the provider backbone toward the correct PE router. An inner VPN or service label remains associated with the customer forwarding context. Core P routers mainly process the outer label, allowing them to forward customer traffic without maintaining customer-specific VPN routes. This two-label model is an important part of scalable MPLS Layer 3 VPN forwarding.

Question 375.

What does VRRP provide to end hosts?

1. A stable virtual default gateway that can survive failure of one physical router
2. Dynamic BGP route reflection
3. MPLS label switching
4. OSPF area summarization

Correct Answer: 1. A stable virtual default gateway that can survive failure of one physical router

Explanation:

VRRP allows multiple routers to share a virtual IP address used by hosts as their default gateway. One router acts as master while backups monitor its availability. If the master fails, an eligible backup can assume the virtual gateway role without requiring hosts to change configuration. This improves first-hop availability. Tracking and preemption can refine which router should be master under different upstream or recovery conditions.

Question 376.

Which VRRP feature can make a preferred higher-priority router resume the master role after it recovers?

1. Route Target import
2. Preemption
3. BFD discriminator
4. LACP hashing

Correct Answer: 2. Preemption

Explanation:

Preemption allows a VRRP router with a higher effective priority to take back the master role after it becomes available. This ensures that the device intended to be primary during normal operation can resume responsibility after a failure. A preemption delay is often useful so the recovering router can reestablish routing and upstream connectivity before taking over. This avoids unnecessary disruptions during the recovery process.

Question 377.

Which Eth-Trunk behavior helps preserve packet ordering within individual traffic flows?

1. Hashing flows consistently onto particular active member links
2. Sending every packet on every member
3. Randomly moving every packet between members
4. Disabling all but one physical interface

Correct Answer: 1. Hashing flows consistently onto particular active member links

Explanation:

Eth-Trunk load balancing commonly uses a hash of selected packet fields to assign a flow to an active member link. Keeping packets from the same flow on the same member helps preserve their ordering. Different flows can hash to different links, providing aggregate bandwidth utilization across the bundle. A single large flow may still be limited to the capacity of one member, depending on the hashing behavior and traffic characteristics.

Question 378.

Which QoS action is used to change a packet’s DSCP value?

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

Correct Answer: 2. Remarking

Explanation:

Remarking changes a traffic-classification field such as the DSCP value in an IP packet. This allows downstream devices to recognize the packet as belonging to a specific QoS class and apply the intended scheduling, policing, shaping, or congestion-avoidance treatment. Remarking is often performed at a trust boundary so untrusted markings can be normalized. It does not change the routing destination or create additional bandwidth.

Question 379.

What is the principal benefit of BFD compared with relying only on default routing-protocol failure timers?

1. Faster detection of forwarding-path failures
2. Automatic MPLS VPN creation
3. Larger BGP routing tables
4. Elimination of routing protocols

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

Explanation:

BFD is optimized for rapid liveness detection. Routing protocols may use relatively conservative Hello, Dead, Keepalive, or Hold timers to reduce control-plane overhead, which can delay failure recognition. BFD can monitor the forwarding path at shorter intervals and notify the associated routing protocol quickly when connectivity fails. The routing protocol still performs route withdrawal or path recalculation. BFD therefore accelerates convergence without replacing routing logic.

Question 380.

Which network-design approach BEST minimizes instability while maintaining redundancy in a large Huawei environment?

1. Redistribute every protocol into every other protocol without filtering
2. Use only one critical uplink per site
3. Avoid monitoring so protocols can converge independently
4. Use hierarchical routing, explicit policies, summarization, redundant paths, controlled redistribution, BFD where needed, and tested failover**

Correct Answer: 4. Use hierarchical routing, explicit policies, summarization, redundant paths, controlled redistribution, BFD where needed, and tested failover

Explanation:

Stable large-scale networks depend on controlled interactions between technologies. Hierarchical routing reduces topology scope, summarization limits unnecessary route detail, and explicit policies prevent accidental route propagation. Redundant devices and links improve availability, while BFD can reduce failure-detection time. Redistribution should be tightly controlled with filtering and tagging. Testing failover scenarios verifies that routing, MPLS, VRRP, link aggregation, and QoS behaviors work together as intended when real failures occur.