Pass the Huawei HCIP-Datacom H12-831_V1.0 Questions and answers with CertsForce

An IS-IS Link State PDU (LSP) contains information describing a router, its network reachability, and its routing topology.

The LSP identifier 0000.0000.0002.00-00 identifies the originating router ' s system ID as 0000.0000.0002. The AREA ADDR field identifies the router ' s IS-IS area as 49.0001, and the IPv6 interface address field identifies 2000:24::2.

However, the IPv6 reachability entries do not establish that exactly four external network segments have been imported.

The displayed entries provide prefix information, route metrics, and multi-topology identifiers. They do not demonstrate four externally redistributed networks.

Determining whether routes were imported requires examining the appropriate reachability attributes and redistribution information.

Therefore, option C is the conclusion that cannot be established from the displayed LSP.

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???? OSPF Area Roles Recap:

Area 1 = Stub➤ Default route is injected by ABR (R2) — ✅ R6 will get a default route.

Area 2 = Totally Stub➤ Default route injected automatically by ABR (R3) — ✅ R4 will get one.

Area 3 = NSSA➤ By default, no default route is injected unless default-information-originate is explicitly configured on the ABR (R1).

???? Therefore:

R5, located in Area 3 (NSSA), will not receive a default route by default.

✅ Final Answer: D. R5

Official Huawei Extract:

" In NSSA areas, default routes are not injected automatically. To provide a default route in NSSA, the ABR must be configured with default-route-advertise or default-information-originate. Stub and totally stub areas receive default routes by default. "

— [Huawei HCIA-Datacom Certification Guide – OSPF Area Types and Route Injection]

OSPF uses Type 7 Link-State Advertisements (LSAs) to describe external routing information originating within a Not-So-Stubby Area (NSSA). An ASBR inside an NSSA can redistribute external routes and advertise them using Type 7 LSAs.

However, Type 7 LSAs have area-local flooding scope. They are distributed only throughout the NSSA in which they originate, not throughout all NSSAs or ordinary OSPF areas.

An NSSA Area Border Router (ABR) can translate eligible Type 7 LSAs into Type 5 AS-External LSAs. These Type 5 LSAs can then be advertised throughout the appropriate non-stub portions of the OSPF autonomous system.

Stub areas do not accept Type 5 external LSAs, and Type 7 LSAs are not flooded into other areas.

Consequently, the statement incorrectly describes the flooding scope of Type 7 LSAs and is FALSE.

HCIP-Datacom-Advanced Routing & Switching Technology V1.0 Training Material.pdf

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Comprehensive and Detailed In-Depth Explanation:

Understanding the IS-IS Topology in the Question:

R1 (Level-1 Router) is connected to R2 (Level-1-2 Router).

R2 connects Level-1 and Level-2 areas, making it an inter-area router.

R3 (Level-2 Router) connects to R2.

The loopback addresses are:

R1: 10.0.1.1/32

R2: 10.0.2.2/32

R3: 10.0.3.3/32

Key Command Used: default-route-advertise always level-1

This command forces R1 to advertise a default route (0.0.0.0/0) to Level-1 routers.

Level-1 routers (like R1) do not have visibility into Level-2 routes unless a default route is provided by an L1-L2 router (R2 in this case).

Analyzing Each Option:

Option A (TRUE):

If R1 pings an unknown address like 10.0.4.4, it will use the default route if available. However, if no such route exists, it will not send any packets.

This behavior is expected, so this statement is true.

Option B (TRUE):

10.0.2.2 (R2) is a Level-1-2 router, and it can communicate with 10.0.3.3 (R3), which is a Level-2 router.

Since R2 and R3 are both in Level-2, they can exchange routes.

So, 10.0.2.2 can ping 10.0.3.3. This statement is true.

Option C (TRUE):

10.0.1.1 (R1) is a Level-1 router, and 10.0.2.2 (R2) is a Level-1-2 router.

Since R2 is Level-1-2, it shares Level-1 routes with R1, allowing communication between R1 (10.0.1.1) and R2 (10.0.2.2).

Therefore, this statement is true.

Option D (FALSE - Correct Answer):

10.0.1.1 (R1) is a Level-1 router, which means it only knows about Level-1 routes.

10.0.3.3 (R3) is a Level-2 router, and its route is only known by Level-2 routers (R2 & R3).

Since Level-1 routers do not learn Level-2 routes directly (unless specific redistribution is done), R1 does not have a route to 10.0.3.3.

Therefore, R1 (10.0.1.1) cannot ping R3 (10.0.3.3), making this statement false.

Conclusion:

The false statement is Option D (10.0.1.1 can ping 10.0.3.3).

Comprehensive and Detailed In-Depth Explanation:

1. Understanding Route Targets (RT) and Route Distribution in MPLS VPN

MPLS Layer 3 VPNs (L3VPNs) use BGP to distribute VPN routes across multiple Provider Edge (PE) routers.

Each VPN instance (VRF) is configured with Route Targets (RTs) to control which VPN routes are imported/exported.

Route Distinguishers (RDs) are unique per VRF but do not affect route selection.

2. Analyzing VPN1 Configuration

VPN1 is exporting routes with the following Route Targets (vpn-target values):

100:1

200:1

300:1

Remote VPNs will import these routes only if their import RT list matches one of the exported RTs.

3. Matching Exported RTs with Import RTs in Remote VPNs

Remote VPN

Import RTs

Matches VPN1 Exported RTs (100:1, 200:1, 300:1)?

Accepts the Route?

VPN1

100:1

✅ Matches 100:1

✅ Yes

VPN2

200:1, 400:1

✅ Matches 200:1

✅ Yes

VPN3

100:1, 300:1

✅ Matches 100:1, 300:1

✅ Yes

VPN4

500:1

❌ No match

❌ No

✅ VPN1, VPN2, and VPN3 accept the route.

❌ VPN4 does not accept the route because 500:1 is not in the export list of VPN1.

Final Conclusion:

✅ Correct Answer: VPN1, VPN2, and VPN3 will accept the route.

❌ VPN4 does not accept the route because there is no matching RT.

Thus, the correct answer is:

✅ A. VPN1: Import RT=100:1

✅ B. VPN2: Import RT=200:1, 400:1

✅ C. VPN3: Import RT=100:1, 300:1

❌ D. VPN4: Import RT=500:1 (No match, does not accept the route).

OSPFv3 operates over IPv6 and uses the IPv6 header directly. It can transmit packets in the following modes:

Multicast: Uses standard multicast addresses such as:

FF02::5 (All OSPF routers)

FF02::6 (All DR/BDR routers)

Unicast: Used for point-to-point neighbor communication when required.

Broadcast: On broadcast-capable networks, such as Ethernet.

✅ Official Reference from Huawei:

" OSPFv3 runs directly on top of IPv6 and uses the IPv6 header for transport. It supports unicast, multicast, and broadcast modes, similar to OSPFv2 but adapted for IPv6. "

— [Huawei HCIA-Datacom Certification Guide – OSPFv3 Fundamentals]

Comprehensive and Detailed In-Depth Explanation:

To determine the correct matches, we need to analyze VLAN aggregation and MUX VLAN behavior in the given topology.

1. Understanding VLAN Aggregation and MUX VLAN Roles

VLAN Aggregation:

Sub-VLANs (e.g., VLAN 10) are part of a Super-VLAN (e.g., VLAN 100) and share a common gateway.

Hosts in the same Sub-VLAN can communicate directly.

MUX VLAN (Multiple User Group VLAN):

Principal VLAN (VLAN 30): Includes servers, accessible by all VLAN types.

Separate VLAN (VLAN 20): Cannot communicate with other Separate VLAN hosts, but can communicate with the Principal VLAN (Server).

Group VLAN (VLAN 10 - Sub-VLANs): Hosts within the same Group VLAN can communicate, and they can also access the Principal VLAN (Server).

2. Analyzing the Connectivity

PC1 (Sub-VLAN 10 - Employee VLAN)

Can communicate with PC2 (same Sub-VLAN).

Can communicate with the Server (VLAN 30 - Principal VLAN).

PC2 (Sub-VLAN 10 - Employee VLAN)

Can communicate with PC1 (same Sub-VLAN).

Can communicate with the Server (VLAN 30 - Principal VLAN).

PC3 (VLAN 20 - Separate VLAN - Guest VLAN)

Cannot communicate with other PCs in Employee VLAN (PC1, PC2) or Guest VLAN (PC4).

Can communicate with the Server (VLAN 30 - Principal VLAN).

PC4 (VLAN 20 - Separate VLAN - Guest VLAN)

Cannot communicate with other PCs in Employee VLAN (PC1, PC2) or Guest VLAN (PC3).

Can communicate with the Server (VLAN 30 - Principal VLAN).

Server (VLAN 30 - Principal VLAN)

Can communicate with all PCs (PC1, PC2, PC3, PC4) because it belongs to the Principal VLAN, which serves all VLANs.

Comprehensive and Detailed In-Depth Explanation:

Understanding the IS-IS Network Structure in the Question:

IS-IS Area IDs and Router Roles

Area 49.0001 (Level-1-2): Contains R1, R2, R4 (all Level-1-2 routers).

Area 49.0002 (Level-1-2 & Level-1): Contains R3 (Level-1-2) and R5 (Level-1 only).

Key Command Used: ipv6 default-route-advertise always level-1

This command forces R4 to advertise a default route (::/0) to all Level-1 routers within its area.

Only Level-1 routers in the same area as R4 will receive the default route.

Level-2 routers do not receive or propagate this default route unless additional configuration is done.

Route Distribution Analysis:

R4 (Level-1-2) is configured to advertise a default route to Level-1 routers.

R1 and R2 (both Level-1-2) are in the same area (49.0001) as R4, so they receive the default route.

R3 (Level-1-2) is in area 49.0002 but connects to R4 (49.0001), meaning it can receive the default route through its Level-1 connection.

R5 (Level-1 only) is in area 49.0002, but R4 does not propagate the default route to another Level-1 area (49.0002).

Since R5 is a Level-1 router and does not have a Level-2 connection, it cannot receive the default route from R4.

Final Conclusion:

✅ R1 receives the default route.

✅ R2 receives the default route.

✅ R3 receives the default route.

❌ R5 does NOT receive the default route.

Thus, the correct answer is: C. R5.

Comprehensive and Detailed In-Depth Explanation:

1. Understanding the Issue of OSPF Type 5 LSAs in a Dual-Homed CE Scenario

OSPF Type 5 LSAs (External LSAs) are used in OSPF to advertise external routes, such as those learned via BGP or redistributed from another protocol.

In a dual-homed CE setup, like the one in the figure, CE2 connects to both PE2 and PE3 using OSPF.

PE2 and PE3 both redistribute BGP routes into OSPF and advertise them to CE2.

CE2 then forwards these LSAs between PE2 and PE3, potentially causing a routing loop because each PE may re-learn its own previously advertised routes.

2. How Route Tags Prevent Loops in OSPF-BGP Redistribution

The route-tag command assigns a tag to redistributed routes.

When a router receives an external OSPF LSA (Type 5), it checks the route tag.

If the route tag matches the locally configured tag, the router ignores the route to prevent loops.

Example Configuration on PE Routers:

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PE2:

router ospf 1

import-route bgp 100 route-tag 65001

PE3:

router ospf 1

import-route bgp 100 route-tag 65001

Both PE2 and PE3 tag their redistributed BGP routes with 65001.

If PE3 receives an LSA from CE2 with the tag 65001, it ignores it (because it knows it originally advertised it).

✅ This prevents OSPF from incorrectly preferring a route that was originally sourced from itself, avoiding routing loops.

3. Evaluating the Answer Choices

✅ TRUE: If the route tag of the received route matches the locally configured tag, the route is ignored, preventing loops.

❌ FALSE: The statement is correct, so False is incorrect.

Thus, the correct answer is: A. TRUE

Final Conclusion:

✅ The statement is TRUE because route tagging is a valid method to prevent OSPF Type 5 LSA loops in dual-homed scenarios.