What Is SFP Port of Gigabit Switch?

Updated on Jan 10, 2022

In the telecommunication industry, SFP ports 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. What is the SFP port of the Gigabit switch? SFP port vs. RJ45 port, what are the differences? And how to connect them? Keep reading to know more.

Figure1: Gigabit Switch with RJ45 Ports and SFP Ports

                                                               Figure1: Gigabit Switch with RJ45 Ports and SFP Ports

What Is SFP Port on a Gigabit Switch?

The SFP port on the network switch is designed for use with small form factor (SFF) connectors, and offers high speed and physical compactness. The SFP port 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 ports, 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 ports, 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 the fiber SFP module is most commonly used for a high-speed fiber uplink over longer distances.

What Is Combo SFP Port?

The 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, the combo port is a compound port that can support two different physical ports, 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 in a Gigabit switch, then the corresponding copper port is automatically disabled and vice versa. The following picture shows the 2 x Combo SFP ports of FS S3410-48TS-P, 48-Port Gigabit switch.

Figure2: Gigabit Switch with 2 x Combo SFP Ports

                                                                         Figure2:  Gigabit Switch with 2 x Combo SFP Ports

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

Figure3: Gigabit PoE+ Switch with 4 x 1Gb SFP Uplinks

                                                                 Figure3: Gigabit PoE+ Switch with 4 x 1Gb SFP Uplinks

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 a built-in port of the Gigabit switch, which follows the 1000BASE-T Ethernet standard. The RJ45 port only supports Ethernet 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: insert a standard Ethernet cable directly to connect these two network switches.

Figure4: S3800-24T4S Stack Switch

                                                                                    Figure4: S3800-24T4S Stack Switch

SFP Port vs. RJ45 Port

Compared with the Ethernet switch using only the RJ45 port, the SFP port switch supports more types of communication cables and longer reaches of links. The SFP port switch 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 using an SFP port or RJ45 port to interconnect Ethernet switches. If you don’t plan to connect the server through optical links in the near future, you will not need an SFP port switch 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 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, the Gigabit SFP port is more flexible than the 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 offers a broad range of copper and fiber SFP modules that are 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 www.fs.com or contact us directly via sales@fs.com.

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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