What Is SFP Port of Gigabit Switch?

April 26, 2018

In the telecommunication industry, SFP port can be found in a variety of network devices, including Ethernet switches, routers, network interface cards (NIC), servers, etc. Modern Gigabit switch is usually designed with two or more SFP ports. So what is SFP port of Gigabit switch? What are the differences between SFP port and RJ45 port of the Gigabit switch? And how to connect them?

RJ45 port and SFP port of Gigabit switch

What Is SFP Port on a Gigabit Switch?

The SFP port is designed for use with small form factor (SFF) connectors, and offers high speed and physical compactness. It enables a Gigabit switch to allow optical or copper links by inserting the corresponding SFP module (fiber SFP or copper SFP). Regardless of the optical port or electrical port link, the only difference is the physical layer (media). When the SFP port is inserted in 1G SFP with electrical port, the network cable (Cat5e/Cat6/Cat7 cable) must be used for data transmission. Whereas, when the SFP port is plugged in Gigabit SFP with optical port, fiber jumpers (LC fiber) need to support fiber connections. Therefore, the RJ45 SFP module is generally used for short range uplinks to connect between an all-SFP distribution switch and an all-copper edge switch, and fiber SFP module is most commonly used for a high-speed fiber uplink over longer distances.

What Is Combo SFP Port?

Combo port is a single interface with dual front ends - RJ45 port or SFP port, so it supports both copper and optical SFP connections. In other words, it is a compound port which can support two different physical, share the same switch fabric and port number. But these two different physical ports cannot be used simultaneously. Each dual combo port is a single interface that offers a choice of two connections: an RJ-45 connection for a copper Ethernet cable and an SFP connection for a fiber optic cable. For instance, the combo SFP port is being used, then the corresponding copper port is automatically disabled and vice versa. The following picture shows the 4*1GE combo ports of FS S3800-24F4S SFP stack switch.

Combo SFP Port on a Gigabit switch

What Is Uplink SFP Port?

An uplink port is a port on which transmit and receive are reversed, which is designed for inner-switch connection with a standard straight-through cable instead of crossover cable. Thus, the uplink port can connect to a regular port of another device. Plug the uplink port of one switch into the standard port of another switch can help expand the network’s size. Most enterprise switches in the market contain 24 RJ45 port with 2 dedicated SFP ports for uplinks or 48 copper port with either 2 or 4 dedicated SFP uplink ports. Each uplink SFP port has two lights that indicate activity and the status of that port. FS.COM is also provides these uplink SFP ports on 8-port and 24-port Gigabit PoE switches for 1 Gigabit per second data rate.

Uplink SFP Port on a Gigabit switch

SFP Port vs. RJ45 Port of Gigabit Switch

In addition to the SFP ports, Gigabit switch generally has several RJ45 ports. Both of them can be transmitted with Gigabit Ethernet. Then what are the differences among SFP port vs. RJ45 port of Gigabit switch?

What Is RJ45 Port on a Gigabit Switch?

The RJ45 port is built-in port of Gigabit switch, which follows the 1000BASE-T Ethernet standard. It only supports RJ45 cables (Cat5e/Cat6/Cat7) for 1Gbit/s transmission, and the distance is limited to 100m (330ft). So 1000BASE-T switch with RJ45 ports can be used in data centers for server switching, LANs, for uplinks from desktop switches or directly to the desktop for broadband application. FS S3800-24T4S stack switch is this kind of 1000BASE-T switch, which comes with a console port, 24 *10/100/1000BASE-T RJ45 ports and 4 *10GbE SFP+ ports. So when connecting two RJ45 port Gigabit switches, there is a simple and straightforward way: inserting a standard Ethernet cable (Cat5/5e/6/6a) directly to connect these two switches.

RJ45 Port on a Gigabit Switch

SFP Port vs. RJ45 Port

Compared with Ethernet switch using only RJ45 port, SFP port switch supports more types of communication cables and longer reaches of links. It is also able to exchange with the port of the 1000BASE-SX, 1000BASE-LX/LH, 1000BASE-ZX or the 1000BASE- BX10-D/U. But for short-distance links on a Gigabit switch, there is no difference to use SFP port or RJ45 port to interconnect switches. If you don’t plan to connect the server through optical links in the near future, you will not need SFP and you can stay with standard 1000BASE-T. The following table lists the RJ45 connection and SFP connection of Gigabit switches:

Parameter SFP Port RJ45 Port
Connection Types
  • RJ45 SFP module + network cable (Cat5e, Cat6 or higher)
  • fiber SFP module + fiber optic cable (SMF fiber / MMF fiber)
network cable (Cat5e, Cat6 or higher)
Max Distance MMF (550m) / SMF (150km) / Cat5 (100m) 100m (330ft)
Data Rate 1000Mbps (1G) 1000Mbps (1G)


SFP port enables Gigabit switches to connect to a wide variety of fiber and Ethernet cables in order to extend switching functionality throughout the network. As a hot-pluggable I/O device, it can support the RJ45 SFP module and fiber SFP module. To this extent, Gigabit SFP port is more flexible than RJ45 port in practical applications. Besides, the combo and uplink SFP port give users the power and flexibility to configure their switches for their unique application requirements. FS.COM offers a broad range of copper and fiber SFP modules that fully compatible with major vendors on the market, which makes us the vendor of choice for optical network components and solutions. For any further information, please visit or contact us directly via

Related Article:

FS S5800-48F4S 10GB SFP Switch for Data Center Access Network

1000BASE-T Switch with SFP Ports Interconnection Methods?


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