Which type of port is used to connect a laptop to an Ethernet port on a Cisco router?

Modern Cisco routers and laptop network interface cards (NICs) support the Auto-MDIX (Automatic Medium-Dependent Interface Crossover) feature. This technology automatically detects the type of device and cable connected and electronically swaps the transmit and receive pairs if necessary. While traditionally, connecting two like devices such as a router and a laptop (both DTE devices) required a crossover cable, Auto-MDIX makes this unnecessary. Therefore, a standard, more common straight-through Ethernet cable can be used to establish the connection. For a field technician, using a straight-through cable is the standard, practical approach for this task on modern equipment.

A. rollover: This specialized cable is used for out-of-band console connections to a device's management port for initial configuration or recovery, not for Ethernet data traffic.
B. fiber: This refers to a fiber-optic cable medium, which is incompatible with the standard copper RJ-45 Ethernet ports found on most laptops and base router models.
D. crossover: This cable type is required only when connecting older devices that do not support the Auto-MDIX feature. It is not the standard choice for modern hardware.

1. Official Vendor Documentation: Cisco, Cisco 4000 Series Integrated Services Routers Data Sheet. Document ID: C22-731639-09. This data sheet confirms that modern routers support Auto-MDIX. Under "Product specifications," the onboard Ethernet ports are listed with the feature "Automatic media-dependent interface crossover (MDI-X)." This enables the use of straight-through cables for connections to PCs.

2. Official Vendor Documentation: Cisco, Catalyst 2960 and 2960-S Switch Software Configuration Guide, 12.2(55)SE. Chapter: "Configuring Ethernet Interfaces," Section: "Configuring Auto-MDIX." The document states, "When you enable auto-MDIX, the interface automatically detects the required cable connection type (straight through or crossover) and configures the connection appropriately." While for a switch, this document explains the Cisco implementation of the feature that is also present on their routers.

3. Peer-Reviewed Academic Publication (Standard): IEEE Std 802.3-2018, IEEE Standard for Ethernet. Section 3, Clause 40.4.4, "Automatic MDI/MDI-X Configuration." This standard defines the mechanism for Auto-MDIX, which allows devices to negotiate the pinout, thus permitting the use of either straight-through or crossover cables regardless of the device type. This is the foundational standard for the technology.