Cisco 2800 Series Integrated Services Routers

Ethernet AUI Port, Pinouts, and Cable Specifications

Cisco - Ethernet AUI Port, Pinouts, and Cable Specifications


This document explains the Ethernet AUI port, the cabling specifications, and the port pinouts.



There are no specific requirements for this document.

Components Used

The information in this document is based on the software and hardware versions:

  • AUI adapter cable: CAB-3CE18=

The information in this document was created from the devices in a specific lab environment. All of the devices used in this document started with a cleared (default) configuration. If your network is live, make sure that you understand the potential impact of any command.


For more information on document conventions, see the Cisco Technical Tips Conventions.

Background Information

For flexibility, some Cisco routers provide a generic AUI connector for Ethernet ports. These AUI ports are designed to connect to an external transceiver for conversion to a specific media type (such as twisted pair, coax, or fiber). The transceiver may either be directly connected to the AUI port or through an AUI Cable as illustrated below:


Cable Specifications

This section explains the Ethernet port and cable specifications.

Ethernet (AUI) Port Pinout (DB-15)

The table below lists the different pins and their appropriate signals.

Pin1 Ethernet Circuit Signal
3 DO-A Data Out Circuit A
10 DO-B Data Out Circuit B
11 DO-S Data Out Circuit Shield
5 DI-A Data In Circuit A
12 DI-B Data In Circuit B
4 DI-S Data In Circuit Shield
2 CI-A Control In Circuit A
9 CI-B Control In Circuit B
1 CI-S Control In Circuit Shield
6 VC Voltage Common
13 VP Voltage Plus
14 VS Voltage Shield (L25 and M25)
Shell PG Protective Ground

1Any pin not referenced is not connected.

Ethernet Version 2 and IEEE 802.3 Physical Characteristics

The table below lists the Ethernet Version 2 and IEEE 802.3 physical characteristics of the Ethernet cable.

  Ethernet IEEE 802.3
10Base5 10Base2 10BaseT
Data rate (Mbps) 10 10 10 10
Signaling method Baseband Baseband Baseband Baseband
Maximum segment length (in meters) 500 500 185 100 (Unshielded twisted pair - UTP)
Media 50-ohm coax (thick) 50-ohm coax (thick) 50-ohm coax (thin) UTP
Topology Bus Bus Bus Star

Ethernet Coaxial-type Connection Limits for 10-Mbps Transmission

The following table lists the Ethernet coaxial-type connection limits for 10-Mbps transmission.

Parameter 10Base5 10Base2
Cable diameter 1 cm (0.4 in) 0.6 cm (0.25 in)
Maximum segment length 500 m (1640 ft.) 152 m (500 ft.)
Maximum network length (with four repeaters) 2500 m (8200 ft.) 762 m (2500 ft.)
Maximum connections (taps per segment) 100 30
Minimum connection (tap) spacing 2.5 m (8.2 ft.) 0.5 m (1.64 ft.)

Related Information

Updated: Jan 30, 2006
Document ID: 46791