ERSPAN on AOS-CX: which encapsulation protocol is used?

ERSPAN on AOS-CX: which encapsulation protocol is used?

• A. On the source AOS-CX switch, the destination specified is the switch to which the administrator's desktop is connected
• B. GRE
• C. VXLAN
• D. UDP

Answer: (B)

ERSPAN transports mirrored Ethernet frames by creating a tunnel that carries them over IP, and the tunnel wrapper used is GRE. GRE encapsulates the entire original frame inside its header, allowing the remote analyzer to receive the exact Ethernet frames as if they were locally observed. VXLAN is an overlay technology tied to UDP-based tunneling for VM networks, not the mechanism ERSPAN uses. UDP is just a transport protocol and does not provide the GRE-style encapsulation that ERSPAN requires. The detail about where the destination is on the source switch describes destination placement, not how the data is encapsulated. So the GRE encapsulation is the correct choice.

ERSPAN transports mirrored Ethernet frames by creating a tunnel that carries them over IP, and the tunnel wrapper used is GRE. GRE encapsulates the entire original frame inside its header, allowing the remote analyzer to receive the exact Ethernet frames as if they were locally observed. VXLAN is an overlay technology tied to UDP-based tunneling for VM networks, not the mechanism ERSPAN uses. UDP is just a transport protocol and does not provide the GRE-style encapsulation that ERSPAN requires. The detail about where the destination is on the source switch describes destination placement, not how the data is encapsulated. So the GRE encapsulation is the correct choice.