Categorize standard connector types based on network media. This chapter describes fiber and copper media connectors and their associated properties. We cover network cable connectors in our Cisco CCNA video and lab course.
Fiber Network Cable Connectors
Depending on the networking devices and interfaces used in the data center, you can use a number of fiber optic cable connectors, as follows:
- ST
- SC
- LC
- FC
- MT-RJ
A relatively old but still used type of fiber connector is the ST (Straight Tip) connector, which is a bayonet-type connector, meaning you have to push it into the transceiver and turn it to activate the integrated lock system. The same process is carried out when unplugging the connector, meaning you cannot just simply pull it out of the network device. An example of ST connectors is shown in Figure 15.1 below:
Figure 15.1 – ST Connectors
ST connectors are usually used on old devices and on devices they need to stay plugged into in the event of an accident. The main disadvantage of ST connectors is their size, as they are bulky compared with newer connector types. Because of this they might not be practical for use in high-cable-density environments.
A newer type of fiber connector is the SC (Subscriber Connector) connector, although people also refer to it as a Standard Connector or Square Connector. These connectors also have a lock system but it is an automatic one and it is not as secure as the ST lock system. An example of an SC connector is shown in Figure 15.2 below:
Figure 15.2 – SC Connector
SC connectors often can be found in pairs of two (one Transmit and one Receive fiber), connected with a plastic bracket, to make installation easier and not to avoid confusion between the Transmit and the Receive sides. Such a connector can be seen in Figure 15.3 below:
Figure 15.3 – SC Double Connector
The latest type of fiber connector is the LC (Lucent/Little/Local Connector) connector. This has replaced older ST and SC models in network environments because of its small size. LC connectors usually can be found in pairs, with a small bracket that unites the Transmit and Receive fibers and that can be installed in a single connection into the network device. These connectors also have a small lock system that automatically activates when it’s plugged in, but it has to be manually disabled when the connector is unplugged by pressing on the upper plastic bracket. LC connectors allow a large amount of fiber to fit in its small space comparing to ST/SC connector types. An example of an LC connector is shown in Figure 15.4 below:
Figure 15.4 – LC Connector
The MT-RJ (Mechanical Transfer-Registered Jack) connector is one of the smallest fiber optic connector types available. It was created to use the same amount of space in a network device as a standard copper RJ45 connector. To achieve this, both the Transmit and the Receive fibers are embedded into a single small enclosure, as can be seen in Figure 15.5 below:
Figure 15.5 – MT-RJ Connector
Copper Connectors
The most common copper cable connector is the RJ45 (Registered Jack 45) connector. This is what most workstations and laptops use to connect to the network infrastructure, and this is what most network devices use to inter-connect when they are in the same location but do not need very high throughput.
The RJ45 is called an 8P8C connector type because it uses 8 positions and 8 conductors and it has 8 pins that connect to each of the 8 wires in a standard twisted-pair Ethernet cable. An example of an RJ45 connector is shown in Figure 15.6 below:
Figure 15.6 – RJ45 Connector
The RJ45 connector is modular, meaning it can be easily inserted into a compatible jack, but it has an automatic security mechanism that prevents it from accidentally being pulled out. When you need to remove it, you have to press the plastic mechanism to deactivate the security lock. Older copper connection types (e.g., telephone systems) had no modularity, as they had to be directly wired into the patch panel or associated system. Unlike those systems, RJ45 connectors provide a high degree of flexibility and modularity.
Another common modular copper connector is the RJ11 connector, which is most often used in telephone connections and is shown in Figure 15.7 below:
Figure 15.7 – RJ11 Connector
The RJ11 is a 6P2C connector type, meaning it has 6 positions and 2 conductors inside it. This makes sense, because telephone lines usually use only two wires so you don’t need to connect all 6 pins in an RJ11 connector. An alternative to this is the RJ14 connector, which is a 6P4C connector type, used in dual-line telephone systems.
One type of connector that is not really used in modern networks is the BNC (Bayonet Neill-Concelman) connector, which was created by Paul Neill and Carl Concelman. This type of connector was created to be used for Ethernet networking over coaxial cable (10Mbps Thinnet). An example of a BNC connector is shown in Figure 15.8 below:
Figure 15.8 – BNC Connector
The coaxial cable is plugged into the jack and then the BNC connector needs to be turned to lock it in. BNC connectors are most often used with RG-58 coaxial cables in 10Base2 networks. Some of the disadvantages of using BNC connectors and coaxial cables include the following:
- They are rigid
- They are bulky and offer limited flexibility
- They are not standardized for high throughput connections
- They often pull loose and disconnect
Even with all these disadvantages, coaxial cables with BNC connectors were the most commonly used media type until twisted-pair cables and RJ45 connectors were developed.
A type of connector used for digital transmission is the F connector, which is often used in cable television systems (see Figure 15.9 below). These connectors and the associated cables are used to carry analog signals, but currently they are often used to transmit digital signals on the same cable for different purposes, including:
- TV signals
- Voice signals
- Internet signals
Figure 15.9 – F Connector
If you are using serial connections, either to plug in an old device (like a printer) or to configure some kind of network equipment using the console port, you must use a DB-9 type serial connector, which is shown in Figure 15.10 below. This is often referred to as an RS-232 (Recommended Standard 232) connection and it has been an industry standard since 1969.
Figure 15.10 – DB-9 Connector
Serial connections are used when communicating to a number of devices, including:
- Modems
- Printers
- Network devices
- Peripheral computer devices
- Industrial devices
Serial connectors are of different sizes, depending on the number of pins they have:
- DB-9/DE-9 (9 pins)
- DB-25 (25 pins)
- DC-37 (37 pins)
- DD-50 (50 pins)
The serial connector most commonly used in modern networks is the DB-9 port, which is associated with a network device (e.g., switch, router, firewall, etc.) configuration port. The other end is plugged into a management workstation from which you can perform command line device administration.
In order to concentrate all network connectivity, data centers’ connectivity racks often contain so-called 110 blocks in which you can punch in the Ethernet wires using a dedicated tool called a punch tool. A 110 block is shown in Figure 15.11 below:
Figure 15.11 – 110 Block
An alternative to using the blocks described above is using patch panels in the data centers to ensure connectivity to the rest of the building. One side of the patch panel features punch down panels, while the other side features standard RJ45 jacks in which you can plug in UTP cables, as shown in Figure 15.12 below. Patch panels are often used to extend connectivity from each floor of the building to the data center, thus connecting all user devices to the network infrastructure.
Figure 15.12 – Patch Panel
Patch panels offer increased flexibility and modularity when trying to connect devices in different parts of a building and they can extend those connections without the need for permanent cabling.
Summary
Depending on the networking devices and interfaces used in the data center, you can use a number of fiber optic cable connectors, as follows:
- ST
- SC
- LC
- FC
- MT-RJ
The latest type of fiber connector is the LC (Lucent/Little/Local Connector) connector. This has replaced older ST and SC models in network environments because of its small size. LC connectors usually can be found in pairs with a small bracket that unites the Transmit and the Receive fibers and that can be installed in a single connection into the network device.
The copper connectors most often used include the following:
- RJ45
- RJ11
- BNC
- F connector
- DB-9 serial connector
In order to concentrate all network connectivity, data centers’ connectivity racks often contain so-called 110 blocks in which you can punch in the Ethernet wires using a dedicated tool called a punch tool.
An alternative to 110 blocks is using patch panels in the data centers to ensure connectivity to the rest of the building. One side of the patch panel features punch down panels, while the other side features standard RJ45 jacks in which you can plug in UTP cables. Patch panels are often used to extend connectivity from each floor of the building to the data center, thus connecting all user devices to the network infrastructure.
Network cable connectors guide.
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