RJ45 Connector: Types, Compatibility and Ethernet Applications

An RJ45 Connector provides the familiar modular interface used to connect copper Ethernet cables to switches, routers, computers, patch panels and other network equipment. However, connectors that appear identical may not suit the same cable.

For example, compatibility can depend on cable category, conductor gauge, insulation diameter, shielding and solid or stranded construction. Furthermore, the connector and crimping tool must suit each other.

For routine equipment and patch-panel connections, RapidConnect Cat 6 Patch Cables provide factory-terminated connectors, 24AWG copper conductors and performance up to 250 MHz.

What Is an RJ45 Connector?

RJ45 is the networking industry’s common name for the modular connector used with balanced copper Ethernet cabling.

The plug normally contains eight positions and eight contacts. Therefore, its physical configuration is commonly described as 8P8C.

An Ethernet cable contains four twisted conductor pairs. Inside the connector, each conductor connects to one contact. As a result, compatible network equipment can transmit data and, where supported, Power over Ethernet through the connection.

RJ45-style connectors commonly appear on:

• Ethernet patch cables
• Network switches
• Routers
• Computers and servers
• Wireless access points
• IP surveillance cameras
• VoIP telephones
• Patch panels
• Telecommunications outlets
• Copper SFP transceivers
• Industrial network equipment

Although these connectors share the same general shape, their performance ratings and cable compatibility can vary considerably.

Is RJ45 the Same as 8P8C?

RJ45 and 8P8C are closely related terms. However, they are not technically identical.

The term 8P8C describes the connector’s physical configuration:

• Eight contact positions
• Eight installed contacts

In contrast, RJ45 originated as a registered-jack interface designation. Nevertheless, RJ45 has become the widely accepted commercial name for the 8P8C modular connector used with Ethernet cabling.

Therefore, this guide uses “RJ45 Connector” because installers, network technicians and equipment suppliers commonly recognise that term.

How Does an RJ45 Ethernet Connection Work?

An RJ45 plug uses eight metallic contacts to connect the cable’s conductors to a compatible jack or equipment port.

When the plug enters a port, its contacts align with spring contacts inside the jack. Consequently, the connection creates eight electrical paths for Ethernet data and compatible PoE power.

A structured cabling channel may include several RJ45-style connections. For example, it may contain:

• A switch-to-patch-lead connection
• A patch-lead-to-patch-panel connection
• A horizontal-cable-to-outlet connection
• An outlet-to-equipment-cord connection
• An equipment-cord-to-device connection

Every connection contributes to the channel’s overall performance. Therefore, a poor termination or incompatible component can affect the complete network connection.

RJ45 Plugs, Jacks and Ports

The term RJ45 Connector may describe several related components.

RJ45 plug

A plug is the male modular connector fitted to the end of a cable. It includes eight contacts and a retaining latch.

Plugs commonly terminate flexible patch leads. However, specialised plugs may also suit solid horizontal or industrial cables.

RJ45 jack

A jack is the female modular connection used in:

• Keystone modules
• Telecommunications outlets
• Patch panels
• Surface-mount boxes
• Couplers

Jacks for permanent cabling commonly use insulation-displacement contacts. In contrast, patch-cable plugs normally use crimped contacts.

RJ45 equipment port

An equipment port is the female connection built into a switch, router, computer or other network device.

Although plugs, jacks and ports use the same mating format, their internal construction and category rating may differ.

RJ45 Connector Categories

RJ45-style connectors are available for Cat5e, Cat 6, Cat6A and other balanced copper categories.

However, one connector does not determine the complete channel category. Instead, the cable, patch panels, outlets, patch leads and workmanship must operate as a coordinated system.

For example:

• A Cat6A plug does not upgrade Cat 6 cable to Cat6A.
• Cat 6 cable fitted with Cat5e hardware does not create a Cat 6 channel.
• A Cat6A patch lead does not upgrade Cat5e permanent cabling.
• A higher-category jack cannot correct poor installation or excessive pair untwisting.

Therefore, every component should suit the required category and network application.

For more information about cable categories and construction, read our Cat 6 Cable guide.

Cat5e, Cat 6 and Cat6A Connector Compatibility

Cat5e, Cat 6 and Cat6A commonly use the same RJ45-style mating interface. Consequently, their plugs can often enter the same equipment ports.

Nevertheless, physical mating does not guarantee cable compatibility or category performance.

Connector selection can depend on:

• Cable category
• Conductor gauge
• Conductor material
• Insulation diameter
• Overall cable diameter
• Solid or stranded construction
• Shielded or unshielded design
• Load-bar requirements
• Termination-tool compatibility

Therefore, do not select a connector solely because its packaging says Cat 6 or Cat6A. Instead, compare the connector specification with the cable datasheet.

Additionally, follow the manufacturer’s conductor-preparation and crimping instructions.

Solid Versus Stranded Conductor Compatibility

Ethernet cables can use solid or stranded copper conductors. However, these constructions generally perform different roles.

Solid conductors

Solid cable commonly suits permanent horizontal cabling. Therefore, it normally terminates onto patch panels, keystone jacks and telecommunications outlets.

Some modular plugs also accept solid conductors. Nevertheless, their contacts must suit the conductor diameter and construction.

Stranded conductors

Stranded conductors contain several fine copper strands. As a result, the cable provides greater flexibility.

Consequently, stranded cable commonly appears in:

• Patch leads
• Equipment cords
• Cabinet connections
• Workstation connections
• Frequently moved equipment

A plug designed for stranded cable may contact the conductor differently from a plug intended for solid cable. Therefore, using the wrong design can cause intermittent contact, conductor damage or inadequate retention.

Conductor Gauge and Insulation Diameter

American Wire Gauge, or AWG, describes conductor size. Generally, a lower AWG number indicates a larger conductor.

For instance, 24AWG conductors are larger than 26AWG or 28AWG conductors. Consequently, a plug designed for one gauge range may not correctly terminate another.

However, conductor gauge does not confirm insulation diameter. Two cables with the same AWG conductors may use different insulation thicknesses.

Connector compatibility should therefore consider:

• Bare conductor diameter
• Insulated conductor diameter
• Jacket diameter
• Maximum cable-entry diameter

If the conductors are too large, they may not enter the plug or load bar. Conversely, undersized conductors may not sit securely beneath the contacts.

Unshielded and Shielded RJ45 Connectors

Unshielded and shielded Ethernet systems use different connector constructions.

Shielded connectors

Shielded RJ45 connectors include metallic screening intended to maintain shield continuity through the connection.

Depending on their design, they may suit F/UTP, U/FTP, S/FTP or other screened cables. However, the connector must provide the correct method for terminating the foil, braid or drain wire.

Furthermore, shielding must form part of a coordinated channel. Compatible cable, plugs, jacks, patch panels and patch leads must maintain the intended shield path.

As a result, installing one metal-covered plug does not create a correctly designed shielded system.

For further information, see our Shielded Ethernet Cable guide.

Unshielded connectors

Unshielded plugs and jacks commonly suit U/UTP cables. They rely on balanced conductor pairs and controlled twisting rather than metallic screening.

Consequently, these connectors are widely used in offices, schools, homes and communications rooms.

Conventional and Pass-Through RJ45 Plugs

RJ45 modular plugs commonly use conventional or pass-through designs.

Conventional plugs

With a conventional plug, the conductors stop inside the connector.

The installer must arrange the wires, trim them evenly and insert them fully. Afterwards, the plug should be inspected before crimping.

A transparent housing helps confirm that each conductor has reached the correct contact position. However, the cable jacket must also enter the plug’s strain-relief area.

Pass-through plugs

With a pass-through plug, the conductors extend through openings at the front. A compatible crimping tool then trims the protruding ends while completing the termination.

Consequently, this design can simplify conductor-order inspection. Nevertheless, it requires a suitable pass-through crimping tool.

The cut ends must also finish correctly. Otherwise, exposed conductor ends or an incomplete trim may affect reliability.

Neither plug design is automatically superior. Therefore, select the system that suits the cable, tooling and installation requirements.

Load Bars and Staggered Conductors

Some higher-performance or larger-diameter connectors use a load bar.

A load bar can:

• Organise the conductors
• Maintain conductor position
• Guide the wires into the plug
• Stagger conductors across two levels
• Accommodate larger insulation diameters

Staggered arrangements can improve conductor separation inside the connector. Consequently, they may help the connector satisfy higher-category performance requirements.

However, load bars add preparation steps. Therefore, installers must follow the specified conductor order and orientation carefully.

RJ45 Pinouts and Colour Codes

An RJ45 pinout defines the order in which the eight conductors connect to the connector contacts.

The two recognised arrangements are:

• T568A
• T568B

Both arrangements use the same four twisted pairs. However, the orange and green pairs occupy different positions.

Neither arrangement is inherently faster. Therefore, use the scheme specified for the project or already established within the existing cabling system.

For complete colour sequences, connector orientation and termination instructions, see the RJ45 Pinout guide.

RJ45 Connectors and Ethernet Speed

An RJ45-style connector does not have one universal Ethernet speed.

Instead, performance depends on:

• Connector category
• Cable category
• Channel length
• Frequency
• Termination quality
• Crosstalk performance
• Connected network equipment

Suitable copper channels may support:

Ethernet application	Common cabling support
100BASE-TX	Cat5e, Cat 6 and Cat6A
1000BASE-T	Cat5e, Cat 6 and Cat6A
2.5GBASE-T	Suitable Cat5e, Cat 6 and Cat6A
5GBASE-T	Suitable Cat5e, Cat 6 and Cat6A
10GBASE-T	Cat6A to 100 metres; Cat 6 under restricted conditions
25GBASE-T and 40GBASE-T	Category 8 over restricted channel lengths

Consequently, a connector that fits a switch port does not automatically support the highest possible data rate.

Moreover, active equipment determines the negotiated speed. For example, connecting Cat6A cable between two Gigabit Ethernet ports will not increase the connection beyond 1 Gbps.

RJ45 Connectors and Power over Ethernet

Compatible RJ45 connections can carry Ethernet data and electrical power simultaneously.

Depending on the PoE type, power may travel through two or four conductor pairs. Therefore, contact quality becomes particularly important.

High contact resistance may contribute to:

• Voltage drop
• Localised heating
• Intermittent power
• Device restarts
• Connector damage
• Unreliable operation

Consequently, every conductor must terminate correctly. In addition, the plug, jack and complete channel must suit the required power level.

For detailed guidance, read our PoE Ethernet Cable guide.

Common RJ45 Compatibility Mistakes

Selecting a plug by category alone

A Cat 6 label does not guarantee that the plug accepts every Cat 6 cable. Therefore, confirm the conductor gauge, insulation diameter and construction.

Using the wrong conductor contact

A stranded-cable plug may not suit a solid conductor. Consequently, the connection can become mechanically or electrically unreliable.

Using an unshielded plug on shielded cable

The cable may transmit data. However, shield continuity will not extend through the connection.

Using one shielded component

A metal plug alone does not create a correctly coordinated shielded channel. Instead, every relevant component must support the shielding design.

Excessively untwisting the pairs

Pair twists help control crosstalk. Therefore, preserve the twists as close as practical to the termination point.

Failing to secure the cable jacket

The connector should grip the outer jacket for strain relief. Otherwise, pulling force transfers directly to the individual conductors.

Reusing a crimped plug

A modular plug should not normally be reused after an unsuccessful crimp. Instead, remove it and install a new compatible connector.

Factory-Terminated Versus Field-Terminated Patch Leads

Field termination can suit specialised lengths, repairs and site-specific applications. However, successful termination requires compatible components, correct tools and careful testing.

Factory-terminated patch leads provide several advantages:

• Controlled conductor preparation
• Consistent connector alignment
• Reliable strain relief
• Reduced field labour
• Lower risk of incorrect pinouts
• Convenient standard lengths
• Repeatable construction

Therefore, factory-made cords generally provide the better option for routine equipment connections.

RapidConnect factory-terminated Cat 6 patch leads are available in multiple lengths and nine colours. Consequently, they support organised switch, patch-panel and workstation connections.

Testing an RJ45 Connection

Visual inspection should form part of every field termination. However, appearance alone cannot confirm electrical performance.

Initially, inspect:

• Conductor colour order
• Contact position
• Jacket retention
• Pair-twist preservation
• Plug condition
• Shield termination, where applicable

Next, use a suitable wiremap tester to check:

• Continuity
• Shorts
• Opens
• Reversals
• Crossed conductors
• Split pairs

Nevertheless, a basic continuity test does not certify Category 6 performance.

Formal certification may also measure insertion loss, return loss, crosstalk, propagation delay and resistance. Therefore, use equipment and test limits appropriate to the permanent link or channel.

Australian Cabling Requirements

Connecting a factory-made patch lead between accessible equipment differs from installing fixed customer cabling through a building.

In Australia, regulated fixed or concealed telecommunications cabling may need to be completed or directly supervised by an appropriately registered cabler.

This can include cabling installed through walls, ceilings, floor spaces and permanent pathways. Furthermore, fixed cabling must follow applicable separation and installation requirements.

Before installing or modifying fixed customer cabling, review the Australian Communications and Media Authority’s Cabling Provider Rules.

Frequently Asked Questions About RJ45 Connectors

How many contacts does an RJ45 Connector have?

An Ethernet RJ45-style connector has eight positions and eight contacts. Therefore, it is commonly described as an 8P8C connector.

Do Cat5e, Cat 6 and Cat6A use the same connector shape?

They commonly use the same mating interface. However, the plug or jack must still suit the cable category and physical construction.

Can I install a Cat6A plug on Cat 6 cable?

It may fit some products, but compatibility is not guaranteed. Furthermore, the Cat6A plug does not upgrade the complete cable or channel.

Are RJ45 plugs suitable for solid and stranded cable?

Some plugs suit solid conductors, while others suit stranded conductors. Additionally, certain designs support both within specified gauge limits.

Does an RJ45 Connector determine Ethernet speed?

No. Instead, speed depends on the complete cable channel and connected equipment.

Does Gigabit Ethernet use all eight contacts?

Yes. Gigabit Ethernet uses all four twisted pairs. Consequently, every conductor must terminate correctly.

Can an RJ45 Connector carry PoE?

Yes. Compatible connectors can carry data and PoE power. However, the complete channel must suit the required power level.

Is T568A faster than T568B?

No. Both arrangements can provide equivalent performance. Therefore, follow the project specification or existing wiring scheme.

Can I reuse a crimped RJ45 plug?

Generally, no. Once crimped, the contacts and strain-relief mechanism have been permanently operated. Therefore, replace an incorrectly terminated plug.

Does continuity testing certify an RJ45 cable?

No. Continuity testing confirms basic conductor paths. However, it does not prove complete category performance.

Choosing the Right RJ45 Connector

The correct RJ45 Connector must suit both the cable and the network application.

First, confirm the required cable category. Next, identify whether the cable uses solid or stranded conductors. Then check the conductor gauge, insulation diameter, overall cable diameter and shielding.

Additionally, the selected plug or jack must suit the termination tooling and required Ethernet or PoE application. Finally, test every field termination before placing it into service.

For standard connections between compatible switches, patch panels, routers, servers and computers, explore RapidConnect Cat 6 Patch Cables. The range combines 24AWG copper construction, UTP twisted pairs, LSZH jackets and performance up to 250 MHz.

For product selection, project quantities or availability, contact Anderson Corporation on 03 9761 7600 or sales@andcorp.com.au.