Difference of Connecting 2 Switches via RJ45 Port or SFP Port


In computer networking realm, Gigabit Ethernet is a version of Ethernet technology broadly used in local area network (LAN) for transmitting Ethernet frames at 1Gbps. Gigabit Ethernet normally employs optical fiber connection to transmit information at a relatively high speed over long distance. For short distance, copper cables and twisted pair connection are used. When it comes to Gigabit Ethernet switch, there are typically two ports as well: RJ45 copper port and SFP fiber port. But do you know the difference when you connect two network switches together via RJ45 port or SFP port? In this article we will introduce Gigabit port vs SFP port of Ethernet Gigabit switch and guide you to choose a proper RJ45 connection or SFP connection.

RJ45 port and SFP port of Ethernet Gigabit switch

RJ45 Port and SFP Port of Gigabit Ethernet Switch

  • RJ45 Port

The RJ45 port of Gigabit Ethernet switch is a built-in port. For purpose of connecting two network switches, you can connect them with two RJ45 ports by merely using one Cat5 or Cat6 network cable. The following table shows the specific rate and bandwidth of this connection:

Shielded level Maximum transfer rate(distance of 100m) Maximum bandwidth
Cat5 network cable Unshielded 1000 Mbps / 1 Gbps 100 MHz
Cat6 network cable Shielded or unshielded 1000 Mbps / 1 Gbps 100 MHz
  • SFP Port

The SFP port of Gigabit Ethernet switch is in line with 1000BASE-T (IEEE 802.3ab) standard. The transmission rate of it can reach 1000Mbps. Built-in SFP ports on switch enable optical or copper links by inserting the corresponding SFP module: fiber SFP or copper SFP. When SFP port is inserted in 1G copper SFP module, the Ethernet copper cables (Cat5e, Cat6 and Cat7) must be used for data transmission. While when SFP port is pl ugged into Gigabit fiber SFP module, fiber optic patch cables (LC fiber) are needed to support connections.

RJ45 Connection and SFP Connection of Gigabit Ethernet Switch

In order to intuitively explain these two connections of RJ45 port and SFP port, we will take UniFi switch as an example to demonstrate the RJ45 copper connection and SFP fiber connection between two switches. The left side is the SFP connection of UniFi switch and the right side is the RJ45 connection. As the article already mentioned above, SFP connection requires the usage of two SFP electrical modules and a Cat5e/Cat6/Cat7 cable or the usage of two SFP optical modules with optical port and a fiber jumper. While RJ45 connection only requires a Cat5e/Cat6/Cat7 cable.

SFP connection and RJ45 connection

RJ45 Connection and SFP Connection: How to Choose?

The performance of RJ45 connection and SFP connection is basically the same, but the SFP port wiring cost is higher. Nevertheless, SFP port is still indispensable since it can support both SFP optical modules with electrical ports and optical ports. What is more, the transmission distance is obviously longer than RJ45 port when using SFP port optical transceiver. In the meanwhile, SFP connection between two switches performs better in practical applications with high flexibility and scalability.


SFP port empowers two Gigabit switches to connect to a wide variety of fiber and Ethernet cables so as to extend the switching functionality throughout the network. However, RJ45 connection still has the advantage of cost effective characteristic. Nowadays, 10GbE switch is becoming a trend. If you are looking for 10Gb network switch: 10Gb fiber switch with SFP ports or 10Gb copper switch with RJ45 port, FS can all fulfill your specific needs.

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