What is promiscuous mode in a virtual switch or port group?

Promiscuous mode in a virtual switch or port group refers to a configuration that allows the virtual network adapter to receive all network traffic on the segment, regardless of the destination address of the packets. By enabling promiscuous mode, a virtual machine (VM) can intercept all packets flowing through its virtual switch, not just those intended for it by the MAC address. This is particularly useful for network monitoring applications, where the need arises to analyze or log all traffic, contributing to tasks like intrusion detection systems and network diagnostics.

This mode contrasts with standard operation, where a VM would only receive traffic specifically aimed at it. The ability to see all traffic can be beneficial, but it also introduces security considerations, as it allows any VM in promiscuous mode access to potentially sensitive information that typically would not be visible to it.

In this context, the other options represent concepts that do not accurately describe promiscuous mode. Blocking all traffic, restricting traffic to specific VLANs, or encrypting transmitted data are different functionalities that do not align with the core purpose of promiscuous mode in a networking environment.