Network cable assignment: color codes, instructions & more

The most important thing in brief:

• ‍Pin assignment is a craft — documentation is responsibility: T568A and T568B are technically equivalent; consistency across the entire network is crucial. In corporate environments with patch panels, VLANs and hundreds of devices, however, the actual risk is not occupancy — but a lack of documentation that triggers hours of troubleshooting in the event of a malfunction.
• ‍Standards require documentation: BSI basic protection (SYS.1.1), ISO/IEC 27001 and DIN EN 50173 require verifiable, up-to-date documentation of the physical network infrastructure. Anyone who is unable to provide complete cabling evidence during an audit risks complaints — regardless of whether the cables are correctly crimped.
• Automation solves the documentation problem: Manual cabling documentation in Excel or Visio is prone to errors and quickly becomes obsolete. Software such as Docusnap automatically records network nodes, switch ports and connections — and keeps documentation permanently up to date without having to manually update every change.

Imagine: In a medium-sized company with 200 jobs, sporadic VoIP outages occur after a break in restructuring. Switches are rebooted, firmware updated, vendor contacted. In the end, the cause is trivial: Five patch panel ports were occupied according to T568B, all network sockets according to T568A. Swapped wire pairs — a crimping error from three years ago, not documented anywhere.

For IT administrators and IT managers, RJ45 pin assignment is not an academic topic. It is the physical basis of the network — and at the same time one of the most common sources of error that occur in ticket systems as 'sporadic connection problems, 'because no one knows anymore what was misplaced and how.

This article explains what you need to know about RJ45 configuration and the T568A and T568B standards — compactly and without detours. And it shows why correct pin assignment is only half the battle: In corporate environments, the structured documentation of network cabling is just as critical as crimping itself.

What is RJ45 pin assignment — and why is it relevant for IT admins?

The network cable layout describes the allocation of the eight cores of a twisted pair cable (CAT5e, CAT6, CAT7) to the eight pins of an RJ45 plug. Four pairs of twisted wires — blue, orange, green, brown — are placed on pins 1—8 according to a defined color code.

Why is this relevant for IT managers? Because in corporate environments, it's not just one cable that is crimped, but dozens or hundreds — by different technicians, at different times, according to different standards. Each deviation is a potential source of error that only manifests itself months later: as a connection interruption, as a PoE failure, as a gigabit breach that cannot be explained.

Pin assignment is not the problem. The problem occurs when no one can understand which port was used according to which standard.

568A vs. T568B: Direct comparison of pin assignments

Both standards were defined by the Electronic Industries Alliance (EIA) and the Telecommunications Industry Association (TIA). They are technically equivalent — the difference lies exclusively in the position of the wire pairs 2 (orange) and 3 (green).

T568A — pin configuration:

• Pin 1: White-green | Pin 2: Green | Pin 3: White-orange | Pin 4: Blue
• Pin 5: White-Blue | Pin 6: Orange | Pin 7: White-Brown | Pin 8: Brown

T568B — pin configuration:

• Pin 1: White-orange | Pin 2: Orange | Pin 3: White-green | Pin 4: Blue
• Pin 5: White-Blue | Pin 6: Green | Pin 7: White-Brown | Pin 8: Brown

For IT admins, the following applies: T568A is common in Europe and corresponds to the historical color code of European telephone cabling. T568B is the de facto international standard, particularly in North America and in corporate networks worldwide. Both comply with ANSI/TIA-568 standards — but never both on the same network at the same time.

RJ45 Color Code Table (T568A & T568B)

pin | T568A | T568B | wire pair

• Pin 1 | White-green | White-orange | pair 3/pair 2
• Pin 2 | Green | Orange | Pair 3/Pair 2
• Pin 3 | White-orange | White-green | pair 2/pair 3
• Pin 4 | Blue | Blue | Pair 1
• Pin 5 | White-Blue | White-Blue | Pair 1
• Pin 6 | Orange | Green | Pair 2/Pair 3
• Pin 7 | White-Brown | White-Brown | Pair 4
• Pin 8 | Brown | Brown | Pair 4

Note for audits: Document not only the standard used, but also which cable category (CAT5e, CAT6, CAT6a) is installed per route. This is relevant for proof of compliance in accordance with DIN EN 50173 and for subsequent bandwidth expansions.

Gigabit Ethernet, PoE, and Crossover: What Admins Need to Know

Fast Ethernet (100Base-TX) only uses two pairs of wires (pins 1/2 and 3/6). Gigabit Ethernet (1000Base-T) and Power-over-Ethernet (PoE in accordance with IEEE 802.3at/bt) require all eight cores — an error with a single pin reduces the connection to 100 Mbps or interrupts the power supply to connected devices (VoIP telephones, WLAN access points, IP cameras).

Crossover cables (one end T568A, one end T568B) are largely obsolete in modern networks, as almost all switches and network cards support Auto-MDI/X. The topic only remains relevant when it comes to legacy infrastructure or troubleshooting in older environments.

Crimping an RJ45 plug: compact guide for corporate use

This short reference is intended for IT administrators who occasionally lend a hand or check technicians.

1. Strip off the cable jacket 2-3 cm — do not damage wire pairs
2. Split pairs of wires — resolve twists of up to 13 mm (CAT6 requirement)
3. Sort cores by selected standard (T568A or T568B) — check color order before crimping
4. Cut wires straight — cable jacket must reach into the plug (strain relief)
5. Insert all eight wires up to the plug tip — copper must be visible at the front
6. Crimp to an audible click — metal contacts must be fully pressed in
7. Test with cable tester — when the straight-through cable is correct, pins 1—8 light up in parallel

Important for practice: Note down which standard was used directly during installation. If you don't, you create the conditions for the three-day debugging described above.

If you regularly assemble network cables yourself, you will find in our article on Patching network cables further information on professional implementation in a corporate environment.

Network cabling in companies: Where technology alone is not enough

In small environments, a self-crimped cable is sufficient. In corporate networks with multiple locations, patch panels, distributors and hundreds of switch ports, correct pin assignment is just the starting point.

The real challenge starts afterwards: Who laid which cable? Which switch port leads to which workstation? Which routes are occupied after T568A, which after T568B? Which cable category is installed on which route?

Without answers to these questions, troubleshooting is a guessing game. According to industry experience, up to 70% of all network problems are due to poor cabling or lack of documentation — not to faulty pin assignment alone, but to lack of traceability.

A correctly crimped infrastructure without documentation is like a data center without an inventory list: In normal operation, everything works — until it stops working.

What a complete network cabling documentation must cover:

• Patch panel layout with port-to-port assignment (including standard used: T568A/B)
• Switch port documentation including VLAN assignment and connected devices
• Cable category (CAT5e, CAT6, CAT6a) and cable type per route
• IP and MAC addresses of all connected devices
• Wiring date and responsible technician
• History of changes for audits and revisions

How to structure and document a complete network closet is shown in our article on Network cabinet cabling.

Documenting structured cabling: Standards & Compliance

IT managers in regulated environments are subject to documentation requirements — not only for operational reasons, but also for legal reasons:

• BSI IT-Grundschutz (SYS.1.1/INF.12): Requires verifiable documentation of the physical network infrastructure including cabling routes, outlets and patch panels
• ISO/IEC 27001 (Appendix A.11): Requires physical security measures and their documentation for critical IT infrastructure
• DIN EN 50173/ISO/IEC 11801: Defines requirements for structured building cabling and its standard-compliant documentation
• DSGVO/IT Security Act: Indirect documentation requirement for proof of technical-organizational measures (TOMs)

What is required in the audit:

• Current, complete overview of all network connections
• Traceability of changes (Who changed what and when?)
• Proof of standard-compliant cabling (DIN EN 50173)
• Documented current state of physical infrastructure

Imagine: Your company is certified according to ISO 27001. The auditor asks for complete documentation of the physical network infrastructure—patch panel usage, switchport allocation, cable categories. How long would it take to compile this overview in your current environment?

Automate network documentation with Docusnap

Manual documentation in Excel spreadsheets or Visio diagrams has two structural problems: It is time-consuming to create — and it is becoming outdated from day one. Every network change, every new switch port, every replaced cable must be repaired manually. In practice, this rarely happens consistently.

Docusnap solves this problem through automation:

• Automatic detection: Docusnap scans the network and records all nodes, switch ports, IP and MAC addresses, and connections — without manual input
• Physical infrastructure: The integrated infrastructure editor graphically depicts patch panels, distribution cabinets and cabling routes and keeps them up to date
• Topology visualization: Automatically generated network plans show the entire physical and logical infrastructure at a glance
• Audit-ready: All data is stored in an audit-proof manner, changes are traceable — ready for BSI, ISO and GDPR audits
• CMDB integration: IT assets, dependencies, and cabling in an ITIL-compliant configuration management database

What that means in practice: An IT administrator at a medium-sized manufacturing company with three locations and 400 workstations previously needed two weeks to update network documentation following a restructuring. With Docusnap, the effort is reduced to an automated scan — the updated documentation is available within hours.

Learn more:

🔗 IT documentation with Docusnap

🔗 Documenting network cabinet cabling

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Explained even more quickly: Watch our Docusnap YouTube video to learn how to efficiently implement your network documentation with Docusnap.

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