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What is the difference between an RJ-45 interface and a fiber optic interface?
Knowledge Base + 2024.01.17

Switch (Switch) means "switch" is a network device used for electrical (optical) signal forwarding. It provides an exclusive electrical signal path for any two network nodes connected to the switch. The most common type of switch is the Ethernet switch. Other common ones are telephone voice switches, fiber optic switches, etc.


Switches are very widely used network equipment, multiple network devices of the local area network, switches are essential equipment.

>>>To learn more RJ45 SFP SFP+ SFP28 XFP QSFP28 port what is the difference

Various switch interfaces

The interface of the switch is very rich, here is some organized information to share with you.

1、RJ-45 interface

This interface is now our most common network equipment interface, commonly known as "crystal head", the technical term for the RJ-45 connector, belonging to the twisted-pair Ethernet interface type.RJ-45 plug can only be inserted in a fixed direction, there is a plastic shrapnel and RJ-45 slot card to prevent falling off.

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This interface can be used in 10Base-T Ethernet, 100Base-TX Ethernet, 1000Base-TX Ethernet, the transmission medium are twisted pair, but according to the different bandwidths of the media have different requirements, especially 1000Base-TX Gigabit Ethernet connection, at least to use the Super Category 5 cable, to ensure stable and high-speed, but also the use of Category 6 cable. Category 6 cable should be used to ensure stable and high speed.

2、SC fiber optic interface

SC fiber-optic interface in the 100Base-TX Ethernet era has been applied, so then known as 100Base-FX (F is the abbreviation of the word fiber optic fiber), but at that time, due to the performance is not more than the twisted-pair cable outstanding but the cost is higher, so it has not been popularized, and now the industry is vigorously promoting Gigabit Ethernet, SC fiber-optic interface is back to be valued.

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There are many types of fiber optic interfaces, SC fiber optic interface is mainly used for local network switching environment, in some high-performance Gigabit switches and routers provide such an interface, it looks very similar to the RJ-45 interface, but the SC interface appears to be flatter, the obvious difference is still inside the contact, if it is a fine 8 copper contacts, it is the RJ-45 interface, if it is a copper column is the SC fiber optic interface.

3、AUI interface

AUI interface is specifically used to connect the thick coaxial cable, early network cards have such interfaces with hubs, switches connected to form a network, now generally not used.

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AUI interface is a "D" type 15-pin interface, previously used in the token ring network or bus-type network, you can use the external transceiver transceiver (AUI-to-RJ-45), to achieve the connection with the 10Base-T Ethernet network.

4、FDDI Interface

FDDI is one of the mature LAN technologies with the highest transmission rate, has the characteristics of timing token protocol, supports a variety of topologies, and the transmission media is optical fiber.

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Fiber Distributed Data Interface (FDDI) is a set of protocols developed by the American National Standards Organization (ANSI) to send digital signals over fiber-optic cables.FDDI uses a dual-ring token, and the transmission rate can reach up to 100 Mbps.

CCDI is a variant of FDDI that uses twisted-pair copper cable as the transmission medium, and data rates are typically 100 Mbps.

FDDI-2 is an extended protocol of FDDI that supports voice, video and data transmission, and is another variant of FDDI called FDDI Full Duplex Technology (FFDT), which utilizes the same network structure as FDDI, but the transmission rate can be up to 200Mbps.

Since the use of optical fiber as a transmission media has many advantages such as large capacity, long transmission distance, and strong anti-interference ability, it is commonly used in metropolitan area networks, backbone networks in campus environments, and environments with multi-building network distribution, so the FDDI interface is more common in network backbone switches, and now with the popularity of Gigabit, some high-end Gigabit switches have also begun to use this kind of interface.

5、Console interface

We know that this interface is used to configure the switch, so only managed switches have it. And also note that not all managed switches have it, that's because there are various ways to configure the switch, such as through the Telnet command line way, Web way, TFTP way and so on. Although theoretically, the basic configuration of the switch must be through the Console (control) port, but some brands of switches in the factory has been configured in the basic configuration, do not have to carry out such as IP address, basic user name and other basic configuration, so this type of managed switches do not need to provide the Console interface, and for the time being, also accounts for the majority. This type of switch usually only needs some advanced configuration through a simple Telnet or Java program on the Web.

Of course, there are some switches still provide a Console interface, but it should be noted that the Console port for switch configuration is not the same for all switches, some use the same RJ-45 type Console interface with Cisco routers, as shown in the figure.

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Some use the same RJ-45 type Console port as Cisco routers, as shown in the picture.

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As you can see from the picture, the Console ports of the two switches are different, the upper picture is a "female" 9-hole "D" shaped interface, while the lower picture is a "male" 9-pin "D" shaped interface, the lower picture is a "male" 9-pin "D" shaped interface. "They are commonly known as "DB-9" ports, but both are used for switch configuration.

Switch Connection Methods

Because the switch is mainly used as a centralized connection for LAN equipment, it is relatively easy to connect the hardware in general, and you usually only need to insert the corresponding transmission media connector into the corresponding switch interface. The following is only a brief introduction to the switch cascade connection method.

This is the most commonly used way to connect multiple switches, which is done through the UpLink port on the switch. It is important to note that switches cannot be cascaded indefinitely; cascading more than a certain number of switches will eventually cause a broadcast storm, resulting in a serious degradation of network performance. Cascading is further categorized into the following two types:

Cascading using common ports

The so-called common port is to connect through one of the common ports of the switch (such as RJ-45 port). It should be noted that the twisted-pair cable used for this connection should be reversed, that is to say, both ends of the twisted-pair cable should be jumpered (pins 1-3 and 2-6 are aligned). The connection schematic is shown in the picture.

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Using Uplink Port Cascading

In all switch ports, a Uplink port is included next to it, as shown in Figure 2. This port is dedicated for uplink connections, and can be connected to any port other than the "Uplink port" on other switches via a straight-through twisted pair cable (note that this is not an interconnection of Uplink ports).

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The connection diagram is shown below.

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