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RJ45 and Ethernet ports often get confused. On a router or PC, the Ethernet port is the jack (network socket), while RJ45 refers to the 8-pin plug inserted into it.
RJ45 Connector
RJ45 stands for Registered Jack 45. It’s an 8P8C modular plug on Ethernet cables, with eight wires in a clear plastic body. Initially designed for telephone wiring, today an RJ45 connector carries high-speed LAN signals (up to 10 Gbps on Cat6a cable).
Ethernet Port
An Ethernet port (also known as a LAN port) is the socket on a device (such as a PC, router, or switch) where an Ethernet cable is plugged in. It’s a rectangular 8-pin jack with a small clip to lock the cable. These ports connect devices to a wired local area network (LAN).
Key Similarities
- Both RJ45 connectors and Ethernet ports serve wired LANs. An Ethernet cable has an RJ45 plug on each end that fits into Ethernet jacks on devices.
- They carry the same signals. A Cat5e or Cat6 cable with RJ45 ends can handle Gigabit (1 Gbps) or even 10 Gigabit Ethernet (Cat6a cable).
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Key Differences
- RJ45 is the name of the 8P8C connector/jack itself. An Ethernet port is the device’s LAN socket. In practice, almost all copper Ethernet ports use RJ45 jacks.
- RJ45 refers to the plug/jack hardware design, whereas “Ethernet port” refers to the device’s functional interface. Other Ethernet interfaces (like SFP fiber ports) exist, but RJ45 is the standard connector for copper networks.
- Note: RJ45 plugs are larger than the old RJ11 phone plugs. A phone cable will fit loosely in an Ethernet port, but a full-size RJ45 cable will not fit in a phone jack.
| Feature | RJ45 Connector | Ethernet Port |
|---|---|---|
| Definition | 8P8C modular plug/jack (Registered Jack 45) | Device-side LAN socket accepting an RJ45 cable |
| Also called | 8P8C jack, network plug | LAN port, network port |
| Pins/Wires | 8 metal contacts for twisted-pair cable | 8-pin female contacts matching an RJ45 plug |
| Common use | Terminates Cat5/Cat6 Ethernet cable ends | On PCs/routers/switches for wired LAN connections |
Real-World Applications
In home or office networks, plugging an RJ45 cable into the Ethernet ports of a router and a computer creates a wired LAN connection. For example, a wired game console or smart TV uses its Ethernet port and an RJ45 cable to connect to the network. In data centers and telecom, switches and patch panels use RJ45/Ethernet ports to link servers and networking equipment. Industrial controllers and robots often feature rugged RJ45 ports that support protocols such as Ethernet/IP or Profinet over Cat5/Cat6 cables.
Romtronic: Custom Solutions and Quality
For custom cabling needs, Romtronic is a manufacturer known for OEM/ODM cable assemblies. They offer tailored RJ45/Ethernet cable assemblies with rigorous testing and quality control (for example, “300% inspection” to ensure zero defects). This focus on custom design and strict QA ensures network cables meet demanding telecom, industrial, and automation standards.
Sam Wu is the Marketing Manager at Romtronic, holding a degree in Mechatronics. With 12 years of experience in sales within the electronic wiring harness industry, he manages marketing efforts across Europe. An expert in cable assembly, wiring harnesses, and advanced connectivity solutions, Sam simplifies complex technologies, offering clear, actionable advice to help you confidently navigate your electrical projects.
