Huawei Updated H12-821_V1.0 Exam Questions and Answers by asiya

Comprehensive and Detailed Step-by-Step Explanation:

1. What is GRE (Generic Routing Encapsulation)?

GRE is a tunneling protocol that allows the encapsulation of various types of packets (e.g., IPv4, IPv6, multicast, etc.) to be transmitted over another protocol (e.g., IP).

GRE is used to create point-to-point connections over heterogeneous networks.

2. Analysis of Each Option:

Option A: GRE is a Layer 2 VPN encapsulation technology.

Incorrect.

GRE operates at Layer 3 (Network Layer) and encapsulates Layer 3 packets. It is not a Layer 2 VPN encapsulation technology like MPLS or Ethernet-over-IP.

Option B: GRE enables encapsulated data packets to be transmitted over another network layer protocol, but cannot encapsulate multicast data.

Incorrect.

GRE supports the encapsulation and transmission of multicast data packets. This is one of its key features, making it suitable for protocols like OSPF and multicast applications.

Option C: GRE tunnels can work with IPsec to ensure the security of multicast services such as voice and video.

Correct.

GRE by itself does not provide encryption or security. However, GRE can work with IPsec to secure the encapsulated traffic, including multicast data, for services like voice and video.

Option D: GRE tunnels can extend the working range of network protocols with hop limits.

Correct.

GRE encapsulates packets, effectively resetting their hop limits and allowing protocols with limited hop counts (e.g., RIP) to work over larger networks.

3. Summary:

The correct options are C and D .

Let’s analyze the process step-by-step:

R1 redistributes the direct route 10.1.1.0/24 into OSPF .

This OSPF route reaches R2 and R3 .

R2 and R3 are in an environment that uses IS-IS towards R4 .

Both R2 and R3 re-advertise this OSPF route into IS-IS toward R4 (bidirectional route redistribution).

On R3 , a route-policy named hcip is applied to control ASE (Autonomous System External) route preference .

The ACL matches the route 10.1.1.0/24 .

The route-policy sets the preference of this ASE route to 14 .

In Huawei VRP , if a route-policy applied via preference ase route-policy matches a route, it modifies the preference value of the redistributed route when it is advertised.

By default:

OSPF ASE routes have a preference of 150 .

But in this case, due to the policy applied, the preference is explicitly changed to 14 on R3 before re-advertising to R4.

So, R4 will install the route 10.1.1.0/24 from R3 with preference 14 , assuming R2 doesn’t provide a better preference.

Reference from Huawei HCIP-Datacom-Core Technology Study Guide:

“You can control the preference of OSPF ASE routes by using a route-policy and applying it with the command preference ase route-policy. When the policy matches, the specified preference is used instead of the default (150).”

(Chapter: OSPF Advanced Features – Section: Route Control and Inter-AS Route Redistribution)

Comprehensive and Detailed Step-by-Step Explanation:

1. What is L2TP (Layer 2 Tunneling Protocol)?

L2TP is a tunneling protocol used to transport Layer 2 frames over IP networks.

It is commonly used to establish VPNs but does not provide built-in encryption or security for the transmitted data.

2. Why L2TP Requires Additional Security Measures:

Since L2TP does not encrypt traffic, it is vulnerable to eavesdropping and tampering.

To secure L2TP tunnels, it is often paired with IPsec, which provides strong encryption and authentication. The combination of L2TP and IPsec is known as L2TP/IPsec .

3. Why the Statement is TRUE:

The statement accurately describes the limitation of L2TP (lack of encryption) and the need for additional security measures like IPsec.