Which of the following descriptions about Linux network devices is correct?

Question

Options

• AThe tap device works on the third floor
• BThe tun device works on the second floor
• Ctun/tap does not send packets through user space programs but sends them to physical media
• Dtun/tap is simply site-to-site or ethernet devices receive packets not from devices in the house but

• A
  6% (2)
• B
  14% (5)
• C
  3% (1)
• D
  78% (28)

Explanation

Note: The answer choices appear to be poorly translated (likely from Chinese), where "floor" means OSI layer, and "in the house" refers to physical hardware on the host.

Option D is correct because tun/tap devices are virtual interfaces that receive packets from user-space programs, not from physical network hardware - that's their defining characteristic and primary use case (e.g., VPN software intercepts and processes the packets in user space before forwarding them).

Why the distractors are wrong:

• A is wrong - tap operates at Layer 2 (Data Link), handling raw Ethernet frames, not Layer 3.
• B is wrong - tun operates at Layer 3 (Network), handling IP packets, not Layer 2.
• C is wrong - it says tun/tap bypasses user space, which is the exact opposite of reality; routing traffic through a user-space program is the entire point of tun/tap.

Memory tip: Think TUN = TUNnel (Layer 3, IP) and TAP = TAP into Ethernet (Layer 2, frames). A handy mnemonic: "TUN handles IPs, TAP handles frames - both let your app play network games." The key differentiator for exams: tun/tap packets always pass through user space, never directly to physical media.

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