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

 

Question 121.

In OSPF, which router is responsible for translating Type 7 LSAs from an NSSA into Type 5 LSAs for other OSPF areas?

1. An appropriate Area Border Router
2. The Designated Router on every Ethernet segment
3. Any internal router in the NSSA
4. A BGP route reflector

Correct Answer: 1. An appropriate Area Border Router

Explanation:

In an NSSA, external routes introduced by an ASBR are represented using Type 7 LSAs. When those routes need to be advertised into the wider OSPF domain, an appropriate ABR performs the translation from Type 7 to Type 5 LSAs. This allows the NSSA to retain stub-like characteristics while still supporting local route redistribution. The DR is responsible for multi-access network representation, not NSSA external-route translation. Understanding the distinction between ABR and ASBR roles is important when troubleshooting OSPF external route propagation.

Question 122.

Which OSPF feature helps prevent unnecessary neighbor formation on a user-access LAN while still allowing the connected subnet to be advertised?

1. Virtual link
2. Passive interface
3. Route reflection
4. MPLS LDP

Correct Answer: 2. Passive interface

Explanation:

A passive OSPF interface suppresses Hello packets and therefore prevents neighbor relationships from forming on that interface. The connected network can still be included in OSPF routing information, depending on the configuration. This is useful on user, server, or access networks where no OSPF neighbor should exist. It reduces unnecessary control traffic and helps protect the routing protocol from accidental adjacency formation. A virtual link solves a different OSPF backbone-connectivity issue, while LDP and route reflection belong to other technologies.

Question 123.

What is the primary purpose of equal-cost multipath routing in OSPF?

1. Encrypt parallel paths
2. Disable route convergence
3. Allow multiple equal-cost paths to the same destination to be used
4. Replace OSPF areas

Correct Answer: 3. Allow multiple equal-cost paths to the same destination to be used

Explanation:

When OSPF calculates two or more paths to the same destination with the same total cost, a router can install multiple equal-cost routes if the platform and configuration permit it. Traffic can then be distributed across those paths, improving bandwidth utilization and providing path redundancy. ECMP does not change the basic SPF calculation; it simply allows more than one best path when their metrics are equal. It should be designed with awareness of traffic hashing and application flow behavior.

Question 124.

A network has two routes to the same prefix: an OSPF route and a BGP route. Which factor is generally considered when selecting between routes learned from different routing protocols?

1. OSPF DR priority only
2. MPLS label value
3. BGP community only
4. Route preference or administrative preference**

Correct Answer: 4. Route preference or administrative preference

Explanation:

When a router learns the same destination prefix from different routing protocols, it commonly compares each route source’s administrative or protocol preference before comparing metrics that are meaningful only within a particular protocol. The preferred route source is then selected for installation in the routing table, assuming the route is otherwise valid. OSPF cost and BGP attributes help choose among routes within their own respective protocols, but they are not usually compared directly against each other across routing protocols.

Question 125.

What is the main purpose of setting a lower route preference value for one routing protocol on Huawei devices?

1. Make routes from that protocol more preferred when competing routes exist
2. Increase the Ethernet MTU
3. Disable route redistribution
4. Increase BGP AS_Path length

Correct Answer: 1. Make routes from that protocol more preferred when competing routes exist

Explanation:

Huawei routing implementations use route preference values to help choose between routes learned from different protocols. In general, a lower preference value indicates a more preferred route source. This is different from some BGP attributes, such as Local Preference, where a higher value is preferred. Administrators must therefore distinguish between protocol preference and protocol-specific metrics. Changing route preference can significantly alter forwarding behavior and should be done only with a clear understanding of the desired routing hierarchy.

Question 126.

Which BGP condition is necessary before a learned route can normally be used for packet forwarding?

1. The route must have the highest MED
2. Its Next_Hop must be resolvable
3. Its AS_Path must be empty
4. It must be learned only through eBGP

Correct Answer: 2. Its Next_Hop must be resolvable

Explanation:

A BGP route can be received and stored in BGP information even if the Next_Hop address is not reachable. However, the router normally needs to resolve that Next_Hop through its routing table before the route can become usable for forwarding. This is a frequent troubleshooting issue in iBGP designs where loopback addresses or external next hops are used. An IGP, connected route, or static route commonly provides the required recursive reachability.

Question 127.

Why is the BGP Local Preference attribute useful in a network with two internet providers?

1. It selects the OSPF DR
2. It creates an MPLS label
3. It can make one provider the preferred outbound path
4. It determines VRRP mastership

Correct Answer: 3. It can make one provider the preferred outbound path

Explanation:

Local Preference is distributed within an autonomous system and is commonly used to control which external exit internal BGP routers prefer. If an organization wants one internet provider to carry normal outbound traffic, routes learned from that provider can be assigned a higher Local Preference than routes from the backup provider. BGP then generally prefers the higher value, assuming earlier decision factors do not override it. This makes Local Preference a powerful tool for outbound BGP traffic engineering.

Question 128.

What is the main purpose of setting MED values on routes advertised to an external BGP neighbor?

1. Increase the local router ID
2. Replace the AS_Path
3. Create a VPN instance
4. Suggest which entry point the neighboring AS should prefer**

Correct Answer: 4. Suggest which entry point the neighboring AS should prefer

Explanation:

MED is commonly used when two autonomous systems have multiple connections and one AS wants to indicate a preferred inbound entry point to the other. Lower MED values are normally considered more attractive when the attribute is compared. MED is advisory, however, because the neighboring AS can apply its own routing policies or attributes that take precedence. It is therefore a useful traffic-engineering signal rather than a guarantee of how another network will route traffic.

Question 129.

Which BGP tool can be used to match a group of prefixes and apply routing actions to them?

1. Routing policy with prefix matching
2. STP root guard
3. DHCP snooping
4. LACP system priority

Correct Answer: 1. Routing policy with prefix matching

Explanation:

BGP routing policies can match prefixes through mechanisms such as IP prefix lists and then apply actions including permit, deny, Local Preference changes, MED changes, community assignment, or other attribute modifications. This gives administrators precise control over route acceptance and advertisement. Structured policies are particularly important at external boundaries because accidental route leaks can have significant consequences. Layer 2 and DHCP security features do not provide BGP route-policy control.

Question 130.

Why are BGP communities useful in large networks?

1. They automatically create OSPF areas
2. They allow many routes to be tagged and handled consistently by policy
3. They replace all prefix lists
4. They encrypt BGP updates

Correct Answer: 2. They allow many routes to be tagged and handled consistently by policy

Explanation:

BGP communities provide scalable policy metadata. Administrators can assign the same community value to many related prefixes and later match that value in route policies rather than writing separate rules for every route. Communities can support traffic engineering, route filtering, classification, and coordination between networks. They do not remove the need for prefix filters in every situation, but they make complex routing policy easier to organize and maintain. Communities are policy tags, not encryption mechanisms.

Question 131.

What is the main role of a Level-1-2 router in an IS-IS network?

1. Connect Level-1 area routing with the Level-2 backbone
2. Operate only as an Ethernet switch
3. Replace the DIS on all segments
4. Provide DHCP services

Correct Answer: 1. Connect Level-1 area routing with the Level-2 backbone

Explanation:

A Level-1-2 IS-IS router participates in both routing levels. It maintains Level-1 information for its local area and Level-2 information for inter-area connectivity. This allows Level-1 routers to reach destinations outside their own area through the Level-1-2 router. The architecture is conceptually hierarchical and helps limit the scope of detailed topology information. The DIS is a separate role used on broadcast networks and is not replaced simply because a router operates at both IS-IS levels.

Question 132.

Which IS-IS mechanism helps routers detect whether a neighboring router is still reachable?

1. BGP Keepalive only
2. IS-IS Hello PDUs
3. MPLS label withdrawal only
4. DHCP Request messages

Correct Answer: 2. IS-IS Hello PDUs

Explanation:

IS-IS routers use Hello PDUs to discover neighbors and maintain adjacency state. On different network types, appropriate IS-IS Hello formats are exchanged so routers can establish and monitor neighbor relationships. If Hellos are no longer received within the expected period, the adjacency can be declared down and the topology updated. This function is similar in purpose to Hello mechanisms in other link-state protocols, although packet formats and operational details differ.

Question 133.

What is the purpose of label push operation in MPLS?

1. Remove all labels from a packet
2. Convert the packet to an Ethernet broadcast
3. Add an MPLS label to the packet before forwarding it into the labeled domain
4. Encrypt the IP payload

Correct Answer: 3. Add an MPLS label to the packet before forwarding it into the labeled domain

Explanation:

At the ingress of an MPLS domain, a router may classify an IP packet into a forwarding equivalence class and push one or more MPLS labels onto the packet. Downstream routers then use those labels for forwarding. Depending on the service, additional labels may represent transport and VPN context. Label push is one of the fundamental MPLS operations, along with swap and pop. It changes forwarding encapsulation but does not provide encryption by itself.

Question 134.

Which MPLS operation commonly occurs on a transit Label Switching Router?

1. DHCP relay
2. OSPF area translation
3. VRRP election
4. Label swap**

Correct Answer: 4. Label swap

Explanation:

A transit MPLS router commonly receives a packet with an incoming label, looks up that label in its forwarding table, replaces it with the appropriate outgoing label, and sends the packet toward the next hop. This process is known as label swapping. The forwarding action is based on the label rather than a conventional destination-IP lookup for that transport context. Push and pop operations normally occur at other points depending on the LSP and service design.

Question 135.

What is the main purpose of Route Targets in MPLS Layer 3 VPNs?

1. Control which VPN routes are imported and exported
2. Make overlapping prefixes unique by themselves
3. Select the spanning-tree root
4. Define physical interface speed

Correct Answer: 1. Control which VPN routes are imported and exported

Explanation:

Route Targets are extended BGP communities used to control VPN route membership and distribution. A VPN instance can export routes with selected Route Targets, while another instance imports routes based on matching values. This allows flexible designs such as full-mesh VPNs, hub-and-spoke VPNs, and shared-services environments. Route Distinguishers serve the separate purpose of making overlapping customer prefixes unique in the provider control plane.

Question 136.

A VRRP master loses its upstream WAN connection but its LAN interface remains up. Which enhancement can help the backup router take over?

1. Increase the master’s priority permanently
2. Track the upstream interface or route and reduce priority when it fails
3. Disable preemption on all devices
4. Increase the OSPF Dead timer

Correct Answer: 2. Track the upstream interface or route and reduce priority when it fails

Explanation:

VRRP by itself may continue to consider a router eligible for mastership as long as the local VRRP interface remains available. Tracking an important uplink, route, or related condition allows the router’s effective VRRP priority to be reduced when upstream connectivity fails. A backup with better connectivity can then become master. This improves end-to-end gateway resilience because first-hop redundancy reflects more than just the state of the local LAN interface.

Question 137.

What is the main purpose of an Eth-Trunk in a campus backbone?

1. Combine multiple Ethernet links into one logical connection for bandwidth and redundancy
2. Replace IP routing
3. Create BGP communities
4. Assign IPv6 addresses

Correct Answer: 1. Combine multiple Ethernet links into one logical connection for bandwidth and redundancy

Explanation:

An Eth-Trunk allows several physical Ethernet interfaces to operate as a single logical link. This can increase aggregate capacity and maintain connectivity if one member link fails. Traffic distribution is usually based on a hashing algorithm so flows are spread across active members. LACP can be used to negotiate and monitor the aggregation. Eth-Trunk technology is useful in campus cores, data centers, and server connections where both capacity and link resilience are important.

Question 138.

Which statement BEST describes traffic shaping?

1. It always drops excess traffic immediately
2. It can buffer traffic exceeding a configured rate and transmit it later
3. It is used only for BGP
4. It replaces packet classification

Correct Answer: 2. It can buffer traffic exceeding a configured rate and transmit it later

Explanation:

Traffic shaping controls the output rate by temporarily buffering packets that arrive faster than the configured transmission rate. The buffered traffic is then sent later as capacity becomes available. This smooths bursts but may introduce delay. Traffic policing behaves differently because excess traffic is typically dropped or remarked rather than buffered for later transmission. Shaping is therefore useful when temporary delay is preferable to packet loss and when sufficient buffer resources exist.

Question 139.

Which technology is commonly combined with a routing protocol when subsecond failure detection is desired?

1. BFD
2. DHCP relay
3. MSTP only
4. Route Target filtering

Correct Answer: 1. BFD

Explanation:

BFD provides rapid forwarding-path failure detection and can work with routing protocols such as OSPF, IS-IS, and BGP. When BFD detects that a peer or path is no longer reachable, the routing protocol can react without waiting for longer native Hello or keepalive timers to expire. BFD itself does not calculate alternative routes; it provides fast liveness information. This combination is valuable in networks that require quick convergence after link or node failures.

Question 140.

Which design principle BEST improves stability in a network combining OSPF, BGP, IS-IS, MPLS, VRRP, and QoS?

1. Redistribute all routes everywhere without filtering
2. Disable redundant paths
3. Place all devices in one broadcast domain
4. Use clear protocol boundaries, hierarchical design, controlled policy, redundancy, monitoring, and tested failure behavior**

Correct Answer: 4. Use clear protocol boundaries, hierarchical design, controlled policy, redundancy, monitoring, and tested failure behavior

Explanation:

A large network is easier to scale and troubleshoot when every technology has a clearly defined role. Hierarchical design limits topology scope, route policies control redistribution and advertisement, and summarization reduces unnecessary routing detail. Redundant links, VRRP, and BFD improve availability when properly tested. MPLS can provide scalable transport and service separation, while QoS provides predictable treatment during congestion. Clear operational boundaries and monitoring prevent interactions among protocols from becoming unpredictable and reduce the chance of routing loops or extended outages.