H12-891_V1.0 Practice Questions

In Huawei’s Free Mobility solution:

Authentication Point (AP): Identifies users and associates them with a Security Group Tag (SGT) upon access.

Policy Enforcement Point (PEP): Enforces policies between different security groups, such as allowing or denying traffic.

Key points:

A is correct — The PEP enforces inter-group access based on defined policies.

B is incorrect — AP and PEP can be on separate devices, offering deployment flexibility.

C is incorrect — The policy enforcement happens at the PEP, not the AP. AP ' s job is to authenticate and tag traffic.

D is correct — AP and PEP can be deployed on different devices.

Correct answers: A, D

Forwarding Equivalence Class (FEC) is a key concept in MPLS (Multiprotocol Label Switching), where packets with the same forwarding characteristics are grouped into an FEC and assigned a label.

Correct Answers (Cannot be Used for FEC Allocation):

A.  

Fragment offset is used for reassembling fragmented IP packets at the receiver side.

It is not relevant for MPLS label assignment.

B.  

MPLS does not classify packets based on application-layer protocols (e.g., HTTP, FTP).

It works mainly at Layer 2 and Layer 3.

Incorrect Answers (Valid FEC Allocation Standards):

C.  

One of the most common MPLS FEC classifications.

Packets with the same destination are grouped into the same FE

C.  

D.  

MPLS uses CoS-based traffic classification (e.g., Exp bits in MPLS headers).

Different CoS levels can be mapped to different labels.

Reference from Huawei HCIE-Datacom Documentation:

Huawei MPLS Technology Guide – FEC and Label Assignment

HCIE-Datacom MPLS VPN Configuration Guide

Understanding EVPN (Ethernet VPN) Label Allocation and ARP Handling

???? What Happens in This Scenario?

1️⃣ CE1 (192.168.1.1) sends an ARP request to discover the MAC address of CE2 (192.168.1.2).

2️⃣ PE1 receives the ARP request and needs to forward it over the EVPN fabric.

3️⃣ To send the broadcast ARP request across the EVPN network, PE1 forwards the packet to PE4 using BUM (Broadcast, Unknown unicast, and Multicast) forwarding.

4️⃣ PE4, as the Designated Forwarder (DF), forwards the ARP request to CE2.

Role of Labels in EVPN VXLAN/MPLS Networks

???? EVPN uses BGP to distribute MAC/IP reachability information using different route types.

✅ EVPN Type 2 Route (MAC/IP Advertisement Route):

Used for MAC-to-IP address mapping announcements.

Ensures remote VTEPs (PE routers) learn MAC-to-IP bindings dynamically.

✅ EVPN Type 3 Route (Inclusive Multicast Route):

Used for BUM traffic (Broadcast, Unknown Unicast, Multicast).

Assigns a multicast label (e.g., 201) to be used for forwarding broadcast packets like ARP requests.

???? In this case:

The label 201 is used for BUM traffic forwarding.

BUM traffic is handled using an EVPN Type 3 route.

Why is the Answer 3?

✅ EVPN Type 3 routes carry labels for BUM traffic, which includes ARP requests.

✅ Label 201 is used for multicast distribution, which is managed by Type 3 routes.

Real-World Application:

VXLAN Data Centers: Uses EVPN Type 3 routes to control BUM traffic efficiently.

Campus Networks: Prevents unnecessary flooding of ARP requests across VXLAN domains.

✅ Reference: Huawei HCIE-Datacom Guide – EVPN BGP Route Types and Multicast Labeling

In OSPF-based SR-MPLS TE, Adjacency Segment Identifiers (Adj-SIDs) are locally assigned by each router for its directly connected interfaces. These labels are allocated from the Segment Routing Local Block (SRLB) configured on the router. By default, Huawei routers use an SRLB range starting at 9000, and Adj-SIDs are assigned sequentially (e.g., 9000, 9001, 9002, etc.) to each adjacency.

For P3, adjacency labels correspond to its outgoing interfaces. Assuming P3 has two adjacencies (e.g., to P2 and P4, as inferred from typical network topologies), it will allocate two unique Adj-SIDs from its SRL

B.  

The first adjacency (e.g., to P2) is assigned the next available label in the SRLB (e.g., 9002).

The second adjacency (e.g., to P4) is assigned the subsequent label (e.g., 9003).

Analysis of Options:

Option B (9002): Likely assigned to P3’s first adjacency (e.g., link to P2).

Option C (9003): Likely assigned to P3’s second adjacency (e.g., link to P4).

Option A (9006) and D (9005): These labels are likely allocated by other routers (e.g., P4 or P5), as they fall outside the sequential range assigned by P3.

Key Points:

Adj-SIDs are local to the router and do not conflict with labels from other nodes.

The sequential allocation depends on the SRLB configuration. If the SRLB starts at 9000, labels 9000 and 9001 may be reserved for other purposes (e.g., node SIDs or reserved blocks), leaving 9002 and 9003 for adjacency labels.

Conclusion: P3 allocates 9002 and 9003 for its two adjacencies. Thus, B and C are correct.