View Full Huawei H12-821 Exam Dumps and Practice Test Dumps.

Question 221. In a BGP/MPLS Layer 3 VPN, which protocol is primarily used between PE routers to exchange VPN routes?

1. STP
2. DHCP
3. MP-BGP
4. VRRP

Correct Answer: 3. MP-BGP

Explanation:

BGP/MPLS Layer 3 VPN uses Multiprotocol BGP (MP-BGP) between Provider Edge routers to distribute VPN routing information. After a PE learns an ordinary IPv4 route from a directly connected CE, it associates the route with VPN-specific information such as a Route Distinguisher and VPN Target. The resulting VPN-IPv4 route can then be advertised to remote PEs through MP-BGP. Huawei describes MP-BGP as the mechanism used across the service-provider backbone to exchange these VPN routes, while MPLS provides the corresponding data-plane forwarding service.

Question 222. What type of route does a CE normally advertise to its directly connected PE in an IPv4 MPLS L3VPN?

1. A standard IPv4 route
2. A VPN-IPv4 route containing an RD
3. An MPLS label-only route
4. An EVPN MAC/IP route

Correct Answer: 1. A standard IPv4 route

Explanation:

The CE normally has no awareness of the provider’s internal MPLS VPN mechanisms. It exchanges standard IPv4 routes with the directly connected PE using a supported routing method such as static routing, OSPF, IS-IS, RIP, or BGP. After receiving the customer route, the PE stores it in the appropriate VPN instance and adds the Route Distinguisher to form a VPN-IPv4 route for distribution across the provider backbone. This separation allows ordinary customer routing equipment to participate without supporting the MPLS VPN control plane itself.

Question 223. After a PE learns an IPv4 customer route from a CE, what is added to make the route unique for MP-BGP VPN distribution?

1. An STP bridge ID
2. A DHCP transaction ID
3. A VRRP virtual address
4. A Route Distinguisher

Correct Answer: 4. A Route Distinguisher

Explanation:

After a PE receives a standard IPv4 customer route, it associates that route with the configured Route Distinguisher (RD) of the VPN instance. The combination creates a VPN-IPv4 route that is unique even if another customer uses exactly the same IPv4 prefix. This is essential because overlapping private address space is common in MPLS VPN deployments. The RD solves the uniqueness problem in the MP-BGP VPN routing system, while VPN Targets determine which VPN instances are allowed to import or export the resulting routes.

Question 224. Which additional information can an ingress PE advertise with a VPN-IPv4 route to a remote PE?

1. STP root priority only
2. VPN Target information and an MPLS label
3. DHCP lease duration only
4. Only the physical CE interface number

Correct Answer: 2. VPN Target information and an MPLS label

Explanation:

Huawei describes the ingress PE as advertising the VPN-IPv4 route through MP-BGP together with information including an Export VPN Target and an MPLS label. The VPN Target is used by remote PEs to determine whether the route belongs in one of their VPN instances. The label supplies VPN-related forwarding information for the data plane. The remote PE can therefore make both a control-plane import decision and a forwarding decision using the attributes distributed with the VPN route. This is a key distinction between ordinary IPv4 BGP routing and MPLS VPN route distribution.

Question 225. What condition is normally required before a remote PE can install a received VPN route into a local VPN instance?

1. The CE must run MPLS
2. The route must have no RD
3. The P router must be a CE
4. The route’s VPN Target must satisfy the local import policy and its next hop must be reachable

Correct Answer: 4. The route’s VPN Target must satisfy the local import policy and its next hop must be reachable

Explanation:

A remote PE does not automatically install every VPN route received through MP-BGP into every VPN instance. It examines VPN Target information and performs the appropriate route import checks. The route must match the receiving VPN instance’s import policy, and the route’s next hop must also be resolvable so traffic can reach the advertising PE. Huawei describes this process as route crossing, tunnel recursion, and route selection before the VPN route is finally installed into the VPN routing table. This mechanism preserves customer isolation while permitting selective VPN connectivity.

Question 226. Which statement BEST describes the role of a PE router in a BGP/MPLS L3VPN?

1. It has no knowledge of customer VPN information
2. It operates only as an Ethernet bridge
3. It maintains VPN-specific routing information and connects customer sites to the provider backbone
4. It must always act as the customer CE

Correct Answer: 3. It maintains VPN-specific routing information and connects customer sites to the provider backbone

Explanation:

The Provider Edge router is where customer VPN processing occurs. It directly connects to one or more CE devices, maintains VPN instances, learns customer routes, converts those routes into VPN routing information, exchanges VPN routes with remote PEs, and applies MPLS VPN forwarding. Huawei contrasts this with P routers, which operate inside the provider backbone and generally do not connect directly to customer CEs or maintain customer-specific VPN instances. Because of these responsibilities, the PE performs much of the control-plane and service-edge processing in an MPLS L3VPN architecture.

Question 227. Which device normally does NOT need to maintain individual customer VPN routing tables in a basic MPLS L3VPN?

1. Provider (P) router
2. Provider Edge router
3. Customer Edge router
4. Route reflector acting for VPNv4 routes

Correct Answer: 1. Provider (P) router

Explanation:

A P router operates in the provider backbone and normally forwards MPLS traffic without maintaining each customer’s VPN routing table. Customer-specific VPN processing takes place primarily on the PE routers. The P router needs sufficient underlay and MPLS forwarding information to transport labeled traffic between PEs, but it does not normally connect directly to customer CE devices or process customer VPN instances. This separation is a major scalability advantage of BGP/MPLS L3VPN because the service-provider core can transport many VPNs without every core router learning every customer prefix.

Question 228. Which routing methods can be used between a PE and a CE in a Huawei MPLS L3VPN?

1. Only BGP
2. BGP, an IGP, or static routing as appropriate
3. Only OSPF
4. Only MPLS LDP

Correct Answer: 2. BGP, an IGP, or static routing as appropriate

Explanation:

Huawei supports multiple methods for PE-CE route exchange. Depending on the deployment, the PE and CE can use BGP, an Interior Gateway Protocol, or static routing, including a default route. This provides flexibility because customer sites differ in complexity and operational requirements. A small branch may need only a static or default route, while a larger enterprise site may run OSPF or BGP with the PE. Regardless of the PE-CE routing method, the CE exchanges conventional customer routes; the PE handles the conversion into VPN routing information for transport across the MPLS backbone.

Question 229. Why does a CE normally not need to support MPLS in a basic BGP/MPLS L3VPN?

1. MPLS VPN processing is handled by the provider-side PE and backbone
2. MPLS can operate only on hosts
3. The CE exchanges only Layer 2 BPDUs
4. The CE must use VXLAN instead

Correct Answer: 1. MPLS VPN processing is handled by the provider-side PE and backbone

Explanation:

In a standard MPLS L3VPN model, the CE sees an ordinary Layer 3 connection to the service provider. It exchanges normal IP routes with the attached PE and forwards normal IP packets toward that PE. The PE then performs VPN-instance lookup, VPN route processing, and MPLS encapsulation required to transport the customer’s traffic across the provider network. Huawei explicitly notes that the CE usually does not perceive the existence of the VPN and does not need MPLS functionality. This simplifies customer-site requirements and keeps MPLS complexity within the provider domain.

Question 230. In a Huawei VPN instance configuration, what is the effect of using vpn-target 100:1 both?

1. It configures only an RD
2. It disables route exchange
3. It configures only the export target
4. It applies the specified VPN Target to both import and export operations

Correct Answer: 4. It applies the specified VPN Target to both import and export operations

Explanation:

The both keyword means the specified VPN Target is used for both export and import behavior in the VPN instance. Routes exported from the VPN can carry that RT, and routes received with a matching RT can be imported into the VPN according to the configured policy. Huawei configuration examples commonly use a command such as vpn-target 100:1 both when two sites belong to the same VPN and should exchange routes symmetrically. More complex designs can configure different import and export targets to implement hub-and-spoke or controlled inter-VPN connectivity.

Question 231. What must be configured between two PEs so they can exchange IPv4 VPN routes using MP-BGP?

1. An STP adjacency
2. A VPNv4 BGP peer relationship with the peer enabled in the VPNv4 address family
3. A DHCP relay relationship
4. An IGMP snooping instance

Correct Answer: 2. A VPNv4 BGP peer relationship with the peer enabled in the VPNv4 address family

Explanation:

To exchange VPN-IPv4 routes, the PEs need a BGP peer relationship and must enable that peer within the VPNv4 address family. Huawei configuration procedures explicitly enter the ipv4-family vpnv4 view and then enable the specified peer for VPNv4 route exchange. Establishing an ordinary IPv4 unicast BGP relationship alone is not enough to exchange VPNv4 NLRI. The PEs also need underlying IP reachability so their BGP session can form and a usable transport tunnel so VPN data traffic can subsequently cross the provider backbone.

Question 232. Why are PE loopback interfaces commonly used as BGP peer endpoints in an MPLS backbone?

1. Loopbacks automatically create VPN Targets
2. Loopbacks disable MPLS
3. A loopback provides a stable logical endpoint that is less dependent on the state of one physical interface
4. BGP cannot use physical interfaces

Correct Answer: 3. A loopback provides a stable logical endpoint that is less dependent on the state of one physical interface

Explanation:

Loopback interfaces are widely used as routing-protocol and BGP peer endpoints because they remain logically available as long as the router itself is operational and the routing system can reach the loopback address. A physical interface address, by contrast, becomes unavailable when that specific interface fails. Huawei L3VPN examples commonly establish PE-to-PE BGP sessions through loopback reachability provided by the backbone IGP. This design improves resilience and separates the control-plane session endpoint from any single physical transport link, especially when multiple paths exist between PEs.

Question 233. What is the PRIMARY purpose of the provider backbone IGP in a conventional MPLS L3VPN?

1. To provide underlay IP reachability between provider routers and PE loopbacks
2. To advertise customer VPN routes directly to CEs in all sites
3. To replace MP-BGP VPN route exchange
4. To assign VPN Targets

Correct Answer: 4. To provide underlay IP reachability between provider routers and PE loopbacks

Explanation:

The provider’s IGP, such as OSPF or IS-IS, supplies the underlay reachability required for the MPLS backbone. Provider routers need routes to infrastructure addresses such as PE and P-router loopbacks so MPLS LSPs and BGP sessions can operate. Customer VPN prefixes are normally distributed between PEs using MP-BGP rather than injected wholesale into the provider IGP. Keeping customer routes out of the backbone IGP improves scalability and maintains a clean separation between infrastructure reachability and VPN service routes. Huawei L3VPN configuration procedures therefore establish IGP reachability before building MPLS and MP-BGP services.

Question 234. What happens if the import VPN Target on a remote PE does not match the export VPN Target attached to a received VPN route?

1. The route is not imported into that VPN instance based on the RT relationship
2. The route automatically becomes a public route
3. The remote PE changes the route’s RD
4. The route is converted into an OSPF Type 1 LSA

Correct Answer: 1. The route is not imported into that VPN instance based on the RT relationship

Explanation:

VPN Targets control membership and route distribution between VPN instances. When a remote PE receives a VPN route, it compares the route’s exported RT values with the import RT values of its local VPN instances. If there is no appropriate match, that VPN instance does not import the route. This mechanism allows the provider to maintain strong logical separation even though all VPN routes may be exchanged through the same MP-BGP infrastructure. Administrators can intentionally use different import and export RT combinations to create complex VPN topologies without changing the customer’s IP prefixes.

Question 235. Why are Route Targets classified as BGP extended communities?

1. They are physical interface identifiers
2. They are MPLS transport labels
3. They are attributes carried with BGP VPN routes to express VPN routing policy
4. They replace the IPv4 destination prefix

Correct Answer: 3. They are attributes carried with BGP VPN routes to express VPN routing policy

Explanation:

A Route Target is implemented as a BGP extended community associated with VPN routing information. Because it travels as an attribute with the VPN route, remote PEs can examine the RT and determine whether the route should be imported into a local VPN instance. This creates flexible policy without requiring unique routing protocols for every customer. Multiple RTs can also be associated with routes where more sophisticated connectivity is required. Route Targets therefore control VPN route membership, whereas Route Distinguishers are used to make otherwise overlapping routes unique in the VPN address family.

Question 236. What is a key reason MP-BGP is used instead of ordinary IPv4 BGP for MPLS VPN route exchange?

1. Ordinary BGP cannot use TCP
2. MP-BGP can carry VPN-specific address families and additional attributes needed for VPN route distribution
3. MP-BGP automatically encrypts customer traffic
4. MP-BGP replaces MPLS forwarding

Correct Answer: 2. MP-BGP can carry VPN-specific address families and additional attributes needed for VPN route distribution

Explanation:

MPLS L3VPN requires more information than an ordinary IPv4 destination prefix. The control plane must distinguish overlapping customer prefixes and distribute attributes such as Route Targets and VPN-related labels. MP-BGP extends BGP so it can carry additional address families, including VPNv4 routes. This allows one BGP infrastructure to transport routing information for many logically separate VPNs. MPLS remains responsible for the labeled data-plane transport, while MP-BGP handles VPN routing information in the control plane. The two technologies therefore perform complementary rather than interchangeable roles.

Question 237. Which statement BEST describes Inter-AS VPN Option B?

1. ASBRs never exchange VPN routes
2. Every customer requires a dedicated physical ASBR interface
3. Only ordinary IPv4 routes are exchanged between ASBRs
4. ASBRs exchange VPNv4 routes using MP-EBGP without requiring a VPN instance for each customer on the ASBR

Correct Answer: 4. ASBRs exchange VPNv4 routes using MP-EBGP without requiring a VPN instance for each customer on the ASBR

Explanation:

Huawei’s Inter-AS VPN Option B allows ASBRs in different provider autonomous systems to establish an MP-EBGP relationship and exchange VPN-IPv4 routes. Unlike approaches that require per-VPN subinterfaces or VPN instances on the ASBR, Option B avoids configuring a customer VPN instance for every VPN on the ASBR. However, the ASBR must maintain and advertise VPNv4 routes, so its VPN routing scale remains an important design consideration. This approach can be useful when a provider VPN service spans multiple autonomous systems and dedicated interfaces for each VPN are impractical.

Question 238. What is an important scalability advantage of Inter-AS VPN Option C compared with Option B in environments containing very large numbers of VPN routes?

1. It removes BGP completely
2. It helps prevent ASBRs from becoming VPN-route bottlenecks by allowing PEs in different ASs to exchange VPN routes more directly
3. It requires every CE to support MPLS
4. It disables labeled routes between autonomous systems

Correct Answer: 2. It helps prevent ASBRs from becoming VPN-route bottlenecks by allowing PEs in different ASs to exchange VPN routes more directly

Explanation:

Huawei identifies Inter-AS VPN Option C as useful when large numbers of VPN routes must cross autonomous-system boundaries. In Option B, ASBRs maintain and advertise the VPNv4 routes, which can make them scalability bottlenecks. Option C establishes the required labeled public-network reachability between autonomous systems and allows PEs in different ASs to establish multi-hop MP-EBGP relationships for VPN route exchange. This reduces VPN route-processing pressure on the ASBRs and improves scalability for large provider deployments, although the design is more complex than simpler inter-AS approaches.

Question 239. After a PE interface is bound to a VPN instance, what configuration concern should an administrator remember?

1. Layer 3 settings such as the interface IP address may need to be configured again
2. The interface can no longer run any routing protocol
3. The VPN instance is automatically deleted
4. The CE must immediately enable MPLS

Correct Answer: 1. Layer 3 settings such as the interface IP address may need to be configured again

Explanation:

Huawei warns that binding a PE interface to a VPN instance changes the interface’s Layer 3 context and can remove existing Layer 3 configuration, including IP addressing and routing-protocol settings. A common configuration sequence is therefore to first bind the interface to the required VPN instance and then configure the customer-facing IP address and any PE-CE routing protocol. Forgetting this behavior can produce a confusing outage because the interface may remain physically Up while losing the Layer 3 parameters required to communicate with the CE.

Question 240. A provider must connect two customer sites using an MPLS L3VPN. Both customers may use overlapping address space, P routers should remain unaware of customer routes, and only sites with matching VPN policy should exchange routes. Which design BEST satisfies these requirements?

1. Put every customer route into the provider IGP
2. Configure one global IP routing table on all PEs and P routers
3. Use separate PE VPN instances, RDs for route uniqueness, RTs for import/export policy, MP-BGP between PEs, and MPLS transport across the core
4. Use STP and VLANs only across the entire provider backbone

Correct Answer: 3. Use separate PE VPN instances, RDs for route uniqueness, RTs for import/export policy, MP-BGP between PEs, and MPLS transport across the core

Explanation:

This design follows the core BGP/MPLS L3VPN architecture. Separate VPN instances isolate customer routing information on the PE. Route Distinguishers make overlapping customer prefixes unique when represented as VPN routes, and Route Targets determine which VPN instances are allowed to exchange those routes. MP-BGP distributes VPN routing information between PEs, while MPLS transports customer packets across the provider backbone. Core P routers therefore need infrastructure and MPLS forwarding information but do not need each customer’s VPN routing table. This division provides isolation, overlapping-address support, policy-controlled connectivity, and scalable provider-core operation.