H12-821_V1-0 practice question 25 of 30

A router performs a lookup in its FIB table for a packet. If the tunnel ID in the matching entry is 0, the packet needs to be forwarded through a tunnel, such as an MPLS tunnel.

Full set: 219 questions

Domain MPLS Principles and Configuration

Answer options
A: TRUE
B: FALSE
Correct Answer:
[FALSE]
Explanation

The statement is incorrect. In a Huawei router's Forwarding Information Base (FIB), a Tunnel ID of 0 (or 0x0) is a special value that indicates the packet should be forwarded using standard IP forwarding, not through a tunnel. This means the router will look up the outbound interface and next-hop information for native IP transmission. A non-zero Tunnel ID is what points to a specific tunnel interface (such as MPLS or GRE), instructing the router to encapsulate the packet and forward it through that designated tunnel.

Why Incorrect

The "True" option is incorrect because it reverses the meaning of the Tunnel ID value. A Tunnel ID of 0 explicitly signifies the absence of a tunnel for forwarding the packet, mandating conventional IP forwarding procedures.

References

1. Huawei HCIP-Datacom-Core Technology V1.0 Training Material.

Reference: In the module "MPLS Basics

" the description of the IP forwarding process based on the FIB table details the role of the tunnel ID (often referred to as a token).

Content: The official courseware explains that when a router looks up a destination in the FIB

the resulting entry contains a token or Tunnel ID. If this value is 0

it indicates that the destination is reachable via a standard IP path (public network instance)

and no tunneling is required. A non-zero value points to a specific tunnel policy or VPN instance

triggering the appropriate encapsulation and forwarding action.

2. Huawei VRP V8R16 Command Reference.

Reference: Documentation for the display fib command.

Content: The output fields for the display fib command

such as Token

explicitly show a value of 0x0 for routes that are forwarded natively over an IP interface. For routes that traverse an MPLS LSP or other tunnels

this field will contain a non-zero hexadecimal value that corresponds to the internal index of that tunnel. This confirms that 0 is the value for non-tunneled forwarding.

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