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

 

Question 341.

In OSPF, what is the main purpose of the MaxAge value for an LSA?

1. Help remove obsolete link-state information from the database
2. Determine the BGP Hold timer
3. Select the VRRP master
4. Set the MPLS label value

Correct Answer: 1. Help remove obsolete link-state information from the database

Explanation:

OSPF LSAs include age information so stale topology data does not remain indefinitely in the link-state database. When an LSA reaches MaxAge, it is treated as expired and can be flushed from the OSPF domain according to normal flooding procedures. This ensures that routers base SPF calculations on current topology information. LSA aging works together with sequence numbers and periodic refresh mechanisms to keep the link-state database synchronized and accurate.

Question 342.

Which OSPF packet is primarily used to summarize the contents of a neighbor’s link-state database during adjacency formation?

1. Hello packet
2. Database Description packet
3. Link State Request packet
4. Link State Acknowledgment packet

Correct Answer: 2. Database Description packet

Explanation:

Database Description packets contain summaries of LSAs in the sender’s link-state database. During the ExStart and Exchange phases, neighboring routers use these summaries to compare their databases and determine which information is missing or outdated. They can then request specific LSAs using Link State Request packets. This staged synchronization process allows OSPF neighbors to build consistent topology databases efficiently before reaching the Full adjacency state.

Question 343.

What is a key difference between OSPF broadcast and point-to-point network types?

1. Point-to-point networks cannot run OSPF
2. Broadcast networks cannot form adjacencies
3. Broadcast networks normally use DR/BDR election, while point-to-point links do not
4. Point-to-point links require BGP

Correct Answer: 3. Broadcast networks normally use DR/BDR election, while point-to-point links do not

Explanation:

On a broadcast multi-access network such as Ethernet, multiple OSPF routers may share the same segment, so the protocol uses DR and BDR election to reduce adjacency complexity. On a point-to-point connection, only two routers share the link, so there is no need for DR or BDR election. Correct network-type configuration is important because it influences neighbor formation, timers, and OSPF control-plane behavior.

Question 344.

Why is an OSPF NSSA useful in some network designs?

1. It disables all external route redistribution
2. It replaces Area 0
3. It allows only Layer 2 traffic
4. It provides stub-like behavior while still allowing local external routes to be introduced**

Correct Answer: 4. It provides stub-like behavior while still allowing local external routes to be introduced

Explanation:

A Not-So-Stubby Area is designed for situations where a branch or limited area should restrict ordinary external LSAs but still needs to redistribute routes from another source locally. The ASBR inside the NSSA originates Type 7 LSAs for those external routes. An appropriate ABR can translate them into Type 5 LSAs for propagation into the wider OSPF domain. This combines reduced external routing detail with controlled redistribution capability.

Question 345.

Which BGP attribute is most appropriate for tagging routes so downstream policy can recognize them?

1. Community
2. Next_Hop
3. Router ID
4. Hold Time

Correct Answer: 1. Community

Explanation:

BGP communities act as policy tags that can be attached to routes without changing the destination prefix itself. Routing policies can later match those communities to alter Local Preference, control route advertisement, classify customer routes, or perform other supported actions. This makes communities highly scalable in complex BGP environments. Next_Hop identifies forwarding reachability, while Router ID and Hold Time serve entirely different protocol functions.

Question 346.

A router has two BGP paths to the same prefix with equal higher-priority attributes. One has a shorter AS_Path. Which path is generally preferred?

1. The path with the longer AS_Path
2. The path with the shorter AS_Path
3. Both paths are always discarded
4. The path with the higher VLAN ID

Correct Answer: 2. The path with the shorter AS_Path

Explanation:

When more influential BGP decision factors are equal, BGP generally prefers the route with the shorter AS_Path. The AS_Path represents the autonomous systems the route has traversed and is also an important loop-prevention mechanism. Administrators can intentionally lengthen an advertised AS_Path through prepending to make one path less attractive to external peers. However, policies such as Local Preference can take precedence over path length.

Question 347.

What is the primary purpose of a BGP peer group or similar peer-template mechanism?

1. Replace routing policies
2. Eliminate the need for autonomous system numbers
3. Apply common configuration efficiently to multiple BGP peers
4. Create MPLS labels

Correct Answer: 3. Apply common configuration efficiently to multiple BGP peers

Explanation:

When many BGP neighbors share similar parameters or policies, configuring each peer independently can create unnecessary complexity and increase the risk of inconsistency. A peer-group or template-based approach allows common attributes, policies, and session settings to be defined once and applied to multiple peers. This improves configuration efficiency and operational consistency. Individual peer-specific settings can still be applied where required.

Question 348.

Why should a BGP route policy usually be tested carefully before deployment?

1. It changes physical cabling
2. It can only affect Layer 2 traffic
3. It permanently disables BGP if incorrect
4. A policy error can unintentionally block, prefer, or advertise large numbers of routes**

Correct Answer: 4. A policy error can unintentionally block, prefer, or advertise large numbers of routes

Explanation:

BGP routing policies can influence route acceptance, advertisement, attributes, and traffic engineering across many prefixes at once. A small logic error may therefore have a large operational impact, such as withdrawing valid routes, leaking unauthorized prefixes, or shifting traffic to an unintended provider. Policies should be reviewed, tested, and deployed with appropriate safeguards. Monitoring route counts and expected path changes after implementation also helps identify unexpected behavior quickly.

Question 349.

In IS-IS, what is the primary purpose of the NET address?

1. Identify the router and its IS-IS area membership
2. Configure a VRRP virtual IP
3. Define a BGP community
4. Assign an MPLS transport label

Correct Answer: 1. Identify the router and its IS-IS area membership

Explanation:

The Network Entity Title is a fundamental IS-IS identifier. It includes an area address, a unique system ID, and an N-selector value. The area portion determines Level-1 area membership, while the system ID uniquely identifies the router within the IS-IS domain. Proper NET planning is important because duplicate system IDs or incorrect area information can create adjacency and routing problems. The NET is not used as a host forwarding address.

Question 350.

What is the primary purpose of the IS-IS system ID?

1. Specify the interface metric
2. Uniquely identify an IS-IS router
3. Determine BGP Local Preference
4. Select the VRRP master

Correct Answer: 2. Uniquely identify an IS-IS router

Explanation:

The IS-IS system ID is part of the router’s NET and must be unique within the routing domain. IS-IS uses this identifier when building link-state information and identifying routers in LSPs and other protocol operations. A duplicate system ID can cause serious topology and adjacency problems because two routers would appear to have the same protocol identity. The system ID is independent of BGP attributes and first-hop redundancy settings.

Question 351.

In MPLS, what does a label push operation do?

1. Add one or more MPLS labels to a packet
2. Remove all IP addressing
3. Disable label forwarding
4. Change the customer’s AS number

Correct Answer: 1. Add one or more MPLS labels to a packet

Explanation:

A label push operation adds an MPLS label or label stack to a packet, commonly when traffic enters an MPLS domain or service. The added label tells downstream MPLS routers how the packet should be forwarded. In MPLS Layer 3 VPNs, more than one label may be pushed, such as a transport label and a VPN service label. Push, swap, and pop are the basic MPLS label operations.

Question 352.

Which MPLS label operation is most commonly performed by a transit core router?

1. Push only
2. Swap
3. Remove the IP header
4. Rewrite the customer prefix

Correct Answer: 2. Swap

Explanation:

A transit MPLS router generally receives a packet with an incoming label, looks up the label in its forwarding table, replaces it with the required outgoing label, and sends the packet toward the next hop. This operation is called label swapping. Ingress routers commonly push labels, while egress or penultimate routers may pop them depending on the design. Swapping allows packets to traverse the MPLS core without repeated customer-IP route lookups.

Question 353.

What is the purpose of a VRF or VPN instance on an MPLS PE router?

1. Configure the provider’s physical fiber
2. Increase BGP timer values
3. Maintain a separate routing and forwarding context for a VPN
4. Elect the IS-IS DIS

Correct Answer: 3. Maintain a separate routing and forwarding context for a VPN

Explanation:

A VRF, or VPN instance, creates a separate routing and forwarding table on a Provider Edge router. Interfaces and routes associated with one customer or VPN can remain isolated from other customers, even when overlapping IP prefixes are used. Route Distinguishers and Route Targets support VPN route exchange through MP-BGP, while the VRF provides the local forwarding separation needed at the PE.

Question 354.

Which MPLS VPN mechanism determines whether a received VPN route should enter a local VRF?

1. Route Distinguisher only
2. OSPF Router ID
3. LDP Hello timer
4. Route Target import policy**

Correct Answer: 4. Route Target import policy

Explanation:

Route Target import policy determines whether a VPN route received through MP-BGP is accepted into a particular VRF. If the route carries a Route Target that matches the VRF’s configured import policy, the route can be imported. Export Route Targets control tags attached to routes leaving the VRF. Route Distinguishers make prefixes unique, but they do not determine VPN membership or import behavior.

Question 355.

What is the main purpose of a VRRP virtual MAC address?

1. Allow the virtual gateway identity to move between VRRP routers without requiring hosts to track a physical router’s MAC address
2. Identify an MPLS VPN
3. Select an OSPF ABR
4. Configure a BGP AS_Path

Correct Answer: 1. Allow the virtual gateway identity to move between VRRP routers without requiring hosts to track a physical router’s MAC address

Explanation:

VRRP represents a logical gateway that can move between participating routers. The virtual MAC address supports this abstraction by allowing hosts to associate the virtual gateway IP with a gateway identity independent of a specific physical router. When mastership changes, the new master can take responsibility for the virtual gateway without requiring hosts to be manually reconfigured. This contributes to transparent first-hop failover.

Question 356.

Why is VRRP tracking useful when the master router loses an upstream path but remains connected to the local LAN?

1. It increases its priority
2. It can lower its effective priority so a healthier backup becomes master
3. It disables all routing protocols
4. It creates an MPLS tunnel

Correct Answer: 2. It can lower its effective priority so a healthier backup becomes master

Explanation:

Without tracking, the current VRRP master may continue forwarding local hosts’ traffic even though it no longer has a usable upstream path. Tracking an important interface, route, or connectivity condition allows the device’s effective priority to decrease when that resource fails. A backup router with better end-to-end connectivity can then become master. This improves availability because VRRP mastership reflects actual forwarding health instead of only LAN interface status.

Question 357.

What is the primary benefit of combining several physical links into an Eth-Trunk?

1. Increased aggregate bandwidth and link redundancy
2. Automatic BGP authentication
3. Replacement of the routing table
4. Automatic MPLS VPN creation

Correct Answer: 1. Increased aggregate bandwidth and link redundancy

Explanation:

An Eth-Trunk combines multiple physical Ethernet interfaces into one logical link. Multiple flows can be distributed across active members, increasing aggregate capacity, and traffic can continue if one member fails. Link aggregation is therefore useful for both performance and resilience. LACP can enhance the design by negotiating and monitoring member links. Individual flow bandwidth still depends on the load-balancing hash and member-link capacity.

Question 358.

Which QoS mechanism decides the order in which packets from different queues are transmitted during congestion?

1. Traffic classification
2. Queue scheduling
3. Route redistribution
4. BFD

Correct Answer: 2. Queue scheduling

Explanation:

Queue scheduling determines how packets waiting in different queues receive access to an interface during congestion. Some scheduling methods can provide strict priority to delay-sensitive traffic, while others share bandwidth according to configured weights or fairness rules. Classification and marking normally occur before packets reach these queues. Scheduling does not increase physical capacity, but it determines how available bandwidth is allocated when demand exceeds that capacity.

Question 359.

What is the main purpose of BFD in a routed network?

1. Detect forwarding-path failures rapidly
2. Calculate OSPF routes
3. Distribute MPLS VPN routes
4. Configure Eth-Trunk hashing

Correct Answer: 1. Detect forwarding-path failures rapidly

Explanation:

Bidirectional Forwarding Detection provides fast liveness monitoring between network endpoints. It can detect a forwarding-path failure quickly and notify protocols such as OSPF, IS-IS, or BGP so they can react and select alternate paths. BFD does not perform route calculation or distribute routing information itself. Its purpose is to complement control-plane protocols by shortening failure-detection time where rapid convergence is required.

Question 360.

Which design practice BEST supports scalability and high availability in a large Huawei network?

1. Use uncontrolled redistribution everywhere
2. Depend on a single gateway and a single uplink
3. Avoid route filtering to simplify configuration
4. Use hierarchical routing, controlled policies, summarized addressing, redundant paths, gateway redundancy, rapid failure detection, and consistent QoS**

Correct Answer: 4. Use hierarchical routing, controlled policies, summarized addressing, redundant paths, gateway redundancy, rapid failure detection, and consistent QoS

Explanation:

A scalable network needs clear routing boundaries and predictable failure behavior. Hierarchical routing and structured addressing support summarization, while route policies and filtering prevent unintended advertisements. Redundant paths, VRRP, Eth-Trunk, and BFD improve service availability and convergence. MPLS can provide scalable transport and VPN separation, while QoS helps protect important applications during congestion. Coordinating these technologies through monitoring and tested operational procedures produces a more stable and manageable network.