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

 

Question 161.

In OSPF, what is the primary purpose of an Area Border Router?

1. Connect different OSPF areas and exchange inter-area routing information
2. Assign IP addresses to end hosts
3. Encrypt all OSPF packets
4. Replace the Designated Router on broadcast segments

Correct Answer: 1. Connect different OSPF areas and exchange inter-area routing information

Explanation:

An Area Border Router has interfaces in more than one OSPF area and connects non-backbone areas to the OSPF backbone. It maintains separate link-state databases for the areas in which it participates and advertises inter-area routing information between them. ABRs are important to OSPF scalability because they help contain detailed topology information within individual areas. They can also perform route summarization where appropriate. An ABR does not provide DHCP services or replace the DR function used on multi-access network segments.

Question 162.

Which OSPF LSA type is used to advertise external routes in normal OSPF areas?

1. Type 2
2. Type 5
3. Type 3
4. Type 1

Correct Answer: 2. Type 5

Explanation:

Type 5 AS External LSAs are originated by an Autonomous System Boundary Router when external routes are redistributed into OSPF. These LSAs can carry destinations learned from other routing protocols or static routing. They are flooded through normal OSPF areas, except into area types that restrict external LSAs. Type 1 and Type 2 LSAs describe intra-area topology, while Type 3 LSAs represent inter-area routes. Understanding LSA types is important when troubleshooting route propagation and area design.

Question 163.

What is the purpose of the OSPF DR priority configured on a broadcast interface?

1. Set the cost of all routes learned through the interface
2. Determine the router ID
3. Influence DR and BDR election on the shared segment
4. Select the OSPF area type

Correct Answer: 3. Influence DR and BDR election on the shared segment

Explanation:

On broadcast multi-access networks, OSPF elects a Designated Router and Backup Designated Router. Interface priority is one of the main factors used during that election, with the higher eligible priority generally preferred. If priorities are equal, the router ID is used as a tiebreaker. An administrator can therefore influence which devices become DR and BDR by configuring priorities appropriately. The priority does not directly alter OSPF path cost or determine the area’s type.

Question 164.

What happens when an OSPF interface is configured with a DR priority of 0 on a broadcast network?

1. The interface cannot send OSPF Hellos
2. The router stops advertising connected routes
3. The router automatically becomes BDR
4. The router becomes ineligible for DR or BDR election on that segment**

Correct Answer: 4. The router becomes ineligible for DR or BDR election on that segment

Explanation:

An OSPF interface priority of 0 makes the router ineligible to become either the Designated Router or Backup Designated Router on that broadcast segment. The router can still participate in OSPF, exchange Hellos, and form the appropriate adjacencies. This setting is useful when administrators want dedicated or more capable devices to handle the DR role. It does not disable OSPF itself or prevent the interface’s network from being advertised.

Question 165.

Which BGP attribute is normally used to influence outbound routing inside the local AS and prefers the highest value?

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

Correct Answer: 1. Local Preference

Explanation:

Local Preference is used within an autonomous system to influence which external path internal BGP routers select for outbound traffic. Higher Local Preference values are generally preferred. For example, routes learned from a primary provider can be assigned a higher Local Preference than routes learned from a secondary provider. This makes the primary provider the favored exit. MED, by contrast, usually prefers lower values and is commonly used to signal an inbound path preference to neighboring autonomous systems.

Question 166.

Which BGP technique can help prevent accidental advertisement of unauthorized prefixes to an external peer?

1. Increase the Hold timer
2. Apply outbound route filtering using prefix lists and route policies
3. Disable AS_Path processing
4. Increase Local Preference for all routes

Correct Answer: 2. Apply outbound route filtering using prefix lists and route policies

Explanation:

Outbound route filtering helps ensure that a BGP router advertises only approved prefixes to an external neighbor. Prefix lists and route policies can match permitted routes and deny everything else. This reduces the risk of route leaks caused by configuration mistakes or unexpected redistribution. Filtering should be applied deliberately at external boundaries and reviewed when address allocations change. Adjusting timers or Local Preference does not provide the same control over which routes are actually advertised.

Question 167.

Why is a full mesh traditionally required between iBGP speakers?

1. iBGP requires direct physical links
2. BGP cannot use loopback addresses
3. Routes learned from one iBGP peer are not normally advertised to another iBGP peer
4. iBGP uses Layer 2 flooding

Correct Answer: 3. Routes learned from one iBGP peer are not normally advertised to another iBGP peer

Explanation:

Traditional iBGP follows a split-horizon-like rule in which a route learned from one iBGP neighbor is not normally advertised to another iBGP neighbor. Therefore, all iBGP speakers historically needed direct BGP sessions with one another to ensure complete route propagation. As networks grew, route reflectors and confederations were introduced to reduce this scaling burden. The full mesh requirement relates to BGP control-plane rules rather than physical topology or loopback usage.

Question 168.

What is the main benefit of using redundant BGP route reflectors?

1. They eliminate the need for an IGP
2. They replace all eBGP sessions
3. They provide DHCP redundancy
4. They reduce dependence on a single route reflector and improve control-plane availability**

Correct Answer: 4. They reduce dependence on a single route reflector and improve control-plane availability

Explanation:

A single route reflector can become an important control-plane dependency for its clients. Deploying redundant route reflectors allows clients to maintain sessions with more than one reflector so route distribution can continue if one fails. The design should be planned carefully to preserve consistent path visibility and avoid unnecessary reflection complexity. Route reflectors improve iBGP scalability, but they do not replace the IGP that provides internal reachability or the eBGP sessions used between autonomous systems.

Question 169.

In IS-IS, what does the overload bit communicate to other routers?

1. The router should generally not be used as a transit path while the condition is active
2. The router should become the DIS immediately
3. The router has no IP addresses
4. All links should receive maximum bandwidth

Correct Answer: 1. The router should generally not be used as a transit path while the condition is active

Explanation:

The IS-IS overload bit can indicate that a router should not normally be used to transit traffic, although its directly connected prefixes may remain reachable. It is useful during events such as startup, maintenance, or situations where the router is not ready to forward transit traffic reliably. Other routers take this information into account during path calculation. This can reduce blackholing during convergence because the router can participate in IS-IS while avoiding transit responsibility until it is fully ready.

Question 170.

Why might an administrator enable the IS-IS overload bit temporarily after a router restart?

1. To disable all interfaces permanently
2. To allow routing information to stabilize before the router carries transit traffic
3. To convert IS-IS to OSPF
4. To increase the MPLS label range

Correct Answer: 2. To allow routing information to stabilize before the router carries transit traffic

Explanation:

After a restart, a router may establish routing adjacencies before every dependent service or forwarding table has fully stabilized. Setting the overload bit temporarily allows the router to advertise its presence while discouraging other routers from using it as a transit node. Once routing, MPLS, or related services are ready, the overload condition can be cleared. This technique can improve network stability during startup and reduce the chance of transient forwarding problems.

Question 171.

What is the primary purpose of MPLS label pop operation?

1. Add another transport label
2. Change a BGP community
3. Remove the top MPLS label from a packet
4. Create a VRRP group

Correct Answer: 3. Remove the top MPLS label from a packet

Explanation:

A label pop operation removes the top label from the MPLS label stack. This commonly occurs near the end of a label-switched path, including during penultimate hop popping where the router before the egress LSR removes the outer transport label. If additional labels remain, such as a VPN service label, the next router can process them. Push, swap, and pop are the three fundamental MPLS label operations used to manipulate the label stack during forwarding.

Question 172.

What is the primary role of the P router in an MPLS Layer 3 VPN?

1. Maintain every customer’s VRF
2. Connect directly to every customer site
3. Import and export customer Route Targets
4. Forward labeled traffic through the provider core without maintaining customer VPN routes**

Correct Answer: 4. Forward labeled traffic through the provider core without maintaining customer VPN routes

Explanation:

A provider core, or P, router primarily transports labeled packets between PE routers. It typically needs reachability and label information for provider infrastructure but does not maintain the customer-specific VRFs and VPN routes held by PE routers. This separation improves scalability because core devices are insulated from the full set of customer routing information. PE routers handle customer connectivity and VPN control-plane functions, while P routers focus on efficient MPLS transport.

Question 173.

Which mechanism allows an MPLS VPN to implement a hub-and-spoke topology?

1. Carefully designed Route Target import and export policies
2. OSPF DR election
3. STP path cost
4. DHCP relay

Correct Answer: 1. Carefully designed Route Target import and export policies

Explanation:

Route Targets control which VPN routes are imported and exported by different VRFs. By assigning different Route Targets to hub and spoke sites, administrators can create a policy in which spokes learn routes through the hub without directly exchanging routes with one another. This provides a flexible hub-and-spoke VPN topology while using the same underlying MPLS infrastructure. The design depends on correct Route Target policy rather than Layer 2 or DHCP mechanisms.

Question 174.

What is the purpose of VRRP priority tracking?

1. Increase OSPF cost automatically
2. Modify a router’s effective VRRP priority based on the status of important resources
3. Create an MPLS label stack
4. Replace the virtual IP address

Correct Answer: 2. Modify a router’s effective VRRP priority based on the status of important resources

Explanation:

VRRP tracking allows the device’s effective priority to change when a monitored interface, route, or other important condition changes state. For example, if the master loses its upstream WAN link, its priority can be reduced so a backup router with healthy upstream connectivity takes over. This makes first-hop redundancy more intelligent because mastership can reflect end-to-end path availability rather than only the local LAN interface state.

Question 175.

Why is LACP useful when several links are bundled into an Eth-Trunk?

1. It negotiates and monitors member participation
2. It automatically creates OSPF areas
3. It provides BGP encryption
4. It replaces IP routing

Correct Answer: 1. It negotiates and monitors member participation

Explanation:

LACP allows devices at both ends of an aggregated link to exchange information about participating interfaces. This helps determine which links can actively join the bundle and makes it easier to detect inconsistent or failed member links. A static Eth-Trunk can aggregate links without LACP, but it lacks the same negotiation capability. LACP improves manageability and resiliency of link aggregation while remaining independent of Layer 3 routing protocols.

Question 176.

What is the purpose of an Eth-Trunk minimum active-link requirement where supported?

1. Force every member link to fail simultaneously
2. Keep the logical trunk operational only when enough member links are active
3. Disable load balancing
4. Convert the trunk to a routed protocol automatically

Correct Answer: 2. Keep the logical trunk operational only when enough member links are active

Explanation:

A minimum active-link requirement can prevent an Eth-Trunk from remaining operational when too few member links are available to provide acceptable capacity or redundancy. For example, if the design requires at least two working links, the logical interface can be treated as unavailable when only one remains. This can trigger higher-layer failover instead of continuing to use a severely degraded path. Such thresholds should be selected according to bandwidth and resiliency requirements.

Question 177.

Which QoS mechanism is BEST suited to enforcing a traffic rate by dropping or remarking packets that exceed the configured profile?

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

Correct Answer: 1. Traffic policing

Explanation:

Traffic policing measures traffic against a configured rate and applies an action when traffic exceeds the allowed profile. Excess packets may be dropped or remarked, depending on the policy. Unlike shaping, policing does not normally rely on buffering large amounts of excess traffic for later transmission. It is therefore useful when a network must enforce bandwidth limits strictly. Classification and marking can be combined with policing to apply different rate policies to different traffic classes.

Question 178.

Which QoS mechanism is most appropriate when excess traffic should be delayed instead of immediately discarded?

1. BGP route dampening
2. Traffic shaping
3. OSPF cost adjustment
4. MPLS label swapping

Correct Answer: 2. Traffic shaping

Explanation:

Traffic shaping controls the transmission rate by buffering packets that temporarily exceed the configured rate and sending them later. This can smooth bursts and reduce packet loss, although it introduces additional delay. It is useful on outbound interfaces when applications can tolerate some buffering. Policing is different because it commonly drops or remarks excess packets rather than delaying them. Shaping must be designed with appropriate buffer and latency considerations.

Question 179.

What is the main benefit of using BFD with VRRP-related upstream routing where applicable?

1. Faster detection of path failures can help the network trigger failover sooner
2. BFD replaces the VRRP virtual IP address
3. BFD assigns VLANs dynamically
4. BFD encrypts gateway traffic

Correct Answer: 1. Faster detection of path failures can help the network trigger failover sooner

Explanation:

BFD can detect forwarding-path failures rapidly and provide failure information to routing or tracking mechanisms. In a resilient gateway design, faster upstream failure detection can contribute to quicker decisions about which router should provide active forwarding. BFD does not replace VRRP itself; VRRP still provides the shared virtual gateway role. Instead, BFD can complement the routing and tracking mechanisms that determine whether a router has healthy upstream connectivity.

Question 180.

Which approach BEST supports predictable operation in a Huawei network using OSPF, BGP, IS-IS, MPLS, VRRP, Eth-Trunk, and QoS?

1. Use uncontrolled redistribution and no filtering
2. Disable redundancy to simplify operations
3. Use one large Layer 2 broadcast domain for everything
4. Define protocol roles clearly, use structured policies and addressing, provide redundancy, monitor failures, and test convergence behavior**

Correct Answer: 4. Define protocol roles clearly, use structured policies and addressing, provide redundancy, monitor failures, and test convergence behavior

Explanation:

Large networks become more reliable when routing, transport, gateway redundancy, link aggregation, and QoS are designed as coordinated but clearly separated functions. OSPF or IS-IS can provide internal reachability, BGP can implement policy control, MPLS can provide scalable service transport, VRRP can protect first-hop gateways, and Eth-Trunk can add link resilience. QoS should follow consistent classification and scheduling rules. Controlled redistribution, route filtering, monitoring, and tested failover behavior reduce the risk of complex interactions causing widespread outages.