passthrough

Passthrough refers to a method by which a signal, data stream, or control command is allowed to pass through a device or system with little or no processing. The goal is to preserve the original content or functionality while enabling access by another component, subsystem, or endpoint.

In computing and virtualization, passthrough describes exposing a hardware device directly to software running in another environment, typically a virtual machine. PCI passthrough (PCIe), using an IOMMU framework such as VT-d (Intel) or AMD-Vi, assigns a physical device to a VM so that the guest OS controls it directly. This provides near-native performance and feature access (for example GPUs or network cards) but requires compatible hardware, careful configuration, and can reduce isolation and hot-plug flexibility.

In networking, IP passthrough or bridge/pass-through modes forward IP traffic from a WAN-facing interface to a downstream device, effectively giving that device a public or configured address. This is common on broadband gateways to enable a connected router or server to handle routing, firewall, or NAT duties themselves. Security and management considerations apply.

In audio/video, HDMI pass-through allows an AV receiver or switch to convey the original video and audio signals from a source to a display, while still supporting features like remote control or device management. Some formats or protocols may be limited by the intermediary device.

In data processing and software pipelines, passthrough describes a pathway that forwards data with little or no transformation, enabling streaming or piping of data between components. Limitations include reduced abstraction, potential security concerns, and compatibility requirements.