Which of the following VPN technologies may have two IP-packet headers in one packet? (Multiple choice)

Question

Options

• AIPsec VPN
• BGRE
• CSSL VPN
• DL2TP
• EMPLS VPN

• A
  71% (17)
• E
  29% (7)

Explanation

All four correct options (IPsec, GRE, SSL, L2TP) can encapsulate an original IP packet inside a new IP packet - creating an outer tunnel header and an inner original header - as part of their tunneling mechanism. IPsec in tunnel mode wraps the entire original IP packet in a new IP envelope; GRE adds a new IP + GRE header around the original; L2TP over UDP/IP carries the original IP packet inside, yielding two IP headers; and SSL VPN in full-tunnel mode encapsulates IP traffic inside a TLS session running over its own IP/TCP stack.

MPLS VPN (E) is the wrong answer because MPLS does not add an IP header - it inserts a label shim header between Layer 2 and Layer 3, forwarding packets by label-switching rather than IP routing. No second IP header is introduced by the MPLS mechanism itself.

Memory tip: Think "double IP = IP-in-IP tunneling." Any protocol that wraps the original IP packet inside a new IP packet gets two headers. MPLS is the outlier because it replaces IP-based forwarding with labels - it subtracts the IP lookup, it doesn't add an IP header. When you see MPLS on a VPN question about extra IP headers, eliminate it immediately.

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