In DU label advertisement mode, if the liberal label retention mode is used, the device reserves labels received from all the LDP peers regardless of whether the LDP peer is the optimal next hop for reaching the destination network.
In MPLS LDP (Label Distribution Protocol), label retention modes control how labels are stored in the Label Forwarding Information Base (LFIB).
DU Label Advertisement Mode (Downstream Unsolicited):
Labels are advertised to all LDP peers without a request.
The receiving router decides which label to use for forwarding.
Liberal vs. Conservative Label Retention:
Liberal Label Retention Mode (Correct Answer)
All received labels from all LDP peers are stored.
Even if a peer is not the optimal next hop, its label is retained.
Allows faster convergence during failures.
Conservative Label Retention Mode
Only the label from the best next-hop peer is stored.
Reduces memory usage but can slow down convergence in case of failure.
Reference from Huawei HCIE-Datacom Documentation:
Huawei MPLS LDP Configuration Guide -- Liberal vs. Conservative Label Retention
HCIE-Datacom Training Material -- Label Advertisement in MPLS Networks
Exhibit:

The following figure shows the inter-AS MPLS VPN Option C (solution 2). RRs are deployed, and no traffic passes through the RRs during forwarding. If a data packet sent from PE2 to 192.168.1.1 carries two labels, which of the following statements about the two labels are correct?
Understanding Inter-AS MPLS VPN Option C (Solution 2)
In MPLS L3VPN Inter-AS Option C, the Route Reflectors (RRs) are used for VPN route distribution but do not participate in data forwarding. The traffic forwarding path is based on MPLS labels assigned at different routers.
Each data packet carries two MPLS labels:
Transport Label (T1) -- Used for forwarding within the backbone.
VPN Label (V1) -- Used for VPN route identification.
Breaking Down the Labels:
VPN Label (V1) -- Allocated by PE1 (Answer: C )
V1 (Inner Label) is the VPN label assigned by the egress PE router (PE1).
This label ensures that when the packet reaches PE1, it knows how to forward the traffic to CE1 (192.168.1.1).
Transport Label (T1) -- Allocated by P2 (Answer: B )
T1 (Outer Label) is the transport label assigned by P2 to forward the packet across the AS core.
This label ensures the packet reaches the next-hop router (ASBR-PE1 in AS100).
Why Are the Other Options Incorrect?
A. 'T1 is allocated by RR2' (Incorrect)
RR2 is used only for route reflection; it does not participate in label allocation or forwarding.
D. 'V1 is allocated by P2' (Incorrect)
P2 is an intermediate router and does not allocate VPN labels.
VPN labels are always assigned by the egress PE router (PE1 in AS100).
Reference: Huawei HCIE Datacom -- MPLS L3VPN Inter-AS Option C
OSPF is deployed on a campus network to implement network interconnection. The LSDB of R2 is shown in the figure.

What can be determined from the LSDB?
To analyze this question, let's break down the key concepts and the given LSDB (Link State Database) information from the figure:
Understanding the LSDB Output:
The output shows the OSPF LSDB on R2 with Router ID 10.1.123.2.
Area 0.0.0.0 (Area 0) is displayed along with several Link State Advertisements (LSAs) including Router LSAs, Network LSAs, and Summary LSAs.
Area 0.0.0.1 (Area 1) also displays Router LSAs and a Type 7 LSA (NSSA LSA) with Link-State ID 0.0.0.0.
An External LSA (Type 5) with Link-State ID 0.0.0.0 and AdvRouter 10.1.123.2 is also present.
Analysis of Each Option:
Option A: Area 1 is an NSSA.
Correct.
The presence of a Type 7 LSA (NSSA LSA) in the database indicates that Area 1 is configured as an NSSA (Not-So-Stubby Area).
NSSA allows the injection of Type 7 LSAs for external routes while blocking Type 5 LSAs from entering the area.
Option B: R2 translates Type 7 default route into Type 5 default route.
Correct.
In an NSSA, if an ABR (like R2) has the NSSA ASBR capability, it will convert Type 7 LSAs to Type 5 LSAs before injecting them into the backbone area (Area 0).
In the LSDB, we see both a Type 7 LSA (NSSA) and a corresponding Type 5 External LSA, confirming that R2 performs this translation.
Option C: R2 advertises the default route in the OSPF process.
Incorrect.
There is no indication that R2 itself is originating the default route.
The Type 7 LSA in Area 1 and the Type 5 LSA in Area 0 only indicate translation from another source, not R2 advertising it directly.
Option D: Area 1 does not have Type 3 LSAs. The possible cause is that R2 filters Type 3 LSAs in the outbound direction of Area 1.
Incorrect.
In an NSSA area, Type 3 LSAs (Inter-Area Prefix LSAs) are typically not generated for external routes.
The absence of Type 3 LSAs in Area 1 is due to the nature of NSSA itself rather than any filtering configured on R2.
Huawei HCIE-Datacom V1.0 Training Materials
Huawei Official Documentation: OSPF Configuration Guide
Huawei OSPFv3 Configuration Guide
RFC 3101 - The OSPF Not-So-Stubby Area (NSSA) Option
HCIE-Datacom Knowledge Base: OSPF Advanced Concepts
===========
Which of the following commands needs to be run in the BGP view to enable a VPN instance to advertise IP routes to the BGP-EVPN address family?
In BGP EVPN configuration for VXLAN-based networks, Huawei uses the command:
[bgp] advertise l2vpn evpn
This command enables the BGP process to advertise routes from a VPN instance into the EVPN (L2VPN) address family, which is used for VXLAN control-plane operations like MAC/IP advertisement.
Option A (advertise irbvfi) --- invalid command.
Option B (advertise vpnv4) --- used for MPLS VPNs, not EVPN.
Option C (advertise irb) --- not a recognized Huawei command.
Option D is the correct and officially used command.
Correct answer: D. advertise l2vpn evpn
You have developed a third-party Portal authentication application and connected it to iMaster NCE-Campus to perform Portal authentication for Wi-Fi users. After connecting to Wi-Fi, a user will be redirected to the login page pushed by the authentication application when visiting any website for the first time.
Comprehensive and Detailed In-Depth
In the Huawei iMaster NCE-Campus solution, when using a third-party Portal authentication application, the following process occurs:
After the Wi-Fi user connects to the network, any attempt to access a website for the first time triggers HTTP redirection.
The user is redirected to the login page provided by the third-party authentication application.
This mechanism ensures that the user authenticates before accessing external resources.
The redirection behavior is consistent with captive portal functionality, which is standard for user authentication on Wi-Fi networks.
Therefore, the statement is TRUE.
Huawei HCIE Datacom Official Certification Guide
Huawei iMaster NCE-Campus Authentication Guide
Captive Portal Authentication Principles
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