Cabling Guide for RJ-45 Console and AUX Ports
(Cisco's 1000 series, 2500 series, and AS5100)

 

Introduction

This document will summarize the cabling requirements for Cisco RJ-45 console and AUX ports. Cisco's 1000 series, 2500 series, and AS5100 all have RJ-45-based console and AUX ports. You can connect either a terminal (DTE) or a modem (DCE) to these ports. Either way, you'll need two components, an RJ-45 cable and an RJ-45-to-DB25 connector.

 

Types of RJ-45 Cabling

There are two types of RJ-45 cabling, straight and rolled. If you hold the two ends of an RJ-45 cable side by side, you'll see eight colored strips, or pins, at each end. If the order of the colored pins is the same at each end, then the cable is straight. If the order of the colors is reversed at each end, then the cable is rolled.

The rolled cable (CAB-500RJ) is standard with Cisco's 2500/CS500.

Note: CAB-OCTAL-ASYNC, the 8-port RJ-45 adapter that is used with the Cisco 2509, 2510, 2511, and 2512, is the same as a rolled cable.

 

Styles of RJ-45-to-DB25 Connectors

There are three styles of RJ-45-to-DB25 connectors, DCE style (modem), DTE style, and DCE style (non modem). Each one has a different role. Generally, DTE is for terminals, DCE (modem) is for modems, and DCE (non-modem) is obsolete.

Note: You can change a DCE style (non modem) to a DCE style (modem) by moving pin 6 to pin 8.

 

Setups That Work

You can't mix and match these components randomly. Only the following combinations work:

  

                        RJ-45       DB25          TO ATTACH
        PORT:           CABLE:      STYLE:        TO A:
        --------------------------------------------------
        AUX/Console     Rolled      DTE           TERMINAL
        AUX/Console     Straight    DCE non-modem TERMINAL
        AUX/Console     Rolled      DCE modem     MODEM

 

These are the only setups that work. If you don't have the components you need, use the chart below to order them.

 

Cisco's RJ-45 Component Guide

This chart summarizes Cisco's RJ-45 components. The first seven entries are DB25 connectors, and the last two are RJ-45 cables. Connectors are described in terms of their sex and their role. For example, an FDTE is a female DTE style connector, an MMOD is a male modem style connector, and so on. Remember, you need shielded cables in order to run at 115.2 Kbps.

  

STYLE  CATALOG PART #  CATALOG DESCRIPTION   LABEL                SHIELDED?                                                     -----
-----  --------------  -------------------   -------------------  ---------
DTE    CAB-25AS-FDTE=  CABLE CONN-FTDTE      29-1026-01/TERMINAL      yes

DTE    CAB-500DTF=     DB-25 CONNECTOR,      29-0810-01/29-DTF-01     no
                       DTE FEMALE

DTE    CAB-500DTM=     DB-25 CONNECTOR,      29-0811-01/29-DTM-01     no
                       DTE MALE

modem  CAB-25AS-MMOD=  CABLE CONN-MODEM      74-0458-01/MODEM         yes
                       TO RJ45 SHLD

modem  CAB-MMOD=       ADP,RJ45/DSUB         29-0881-01/29-MMOD-01    no

DCE    CAB-500DCF=     DB-25 CONNECTOR,      29-0809-01/29-DCF-01     no
(non modem)            DCE FEMALE

DCE    CAB-500DCM=     DB-25 CONNECTOR,      29-0808-01/29-DCM-01     no
(non modem)            DCE MALE

NA     Rolled Cable    CABASY,RJ45 ROLLED,   72-0876-01/CAB-500RJ     NA
                       MODULAR

NA     Straight Cable  -not in  catalog-     31-0756-01               NA

 

RJ-45 Port Pinouts

This chart shows the pinouts for RJ-45 console and AUX ports. The console port does not use RTS/CTS.

  

Console/Auxiliary Port (DTE)
----------------------------
Pin  Signal     Input/Output
----------------------------
1    RTS        Output
2    DTR        Output
3    TXD        Output
4    GND        -
5    GND        -
6    RXD        Input
7    DSR        Input
8    CTS        Input

 

RJ-45 Adapter Pinouts

This chart shows the pinouts for RJ-45 adapters.

  

Cable
RJ-45 Pins   DTE style   DCE style   DCE style
                         (modem)    (non modem)
------------------------------------------------
1            4           5           5
2            20          8           6
3            2           3           3
4            7           7           7
5            7           7           7
6            3           2           2
7            6           20          20
8            5           4           4

 

This chart shows suggested DB-25 to DB-9 adapter pinouts, if you need a DB-9 connector.

  

DB-25 Pin   Signal   DB-9 Pin
-----------------------------
2           TXD      3
3           RXD      2
4           RTS      7
5           CTS      8
6           DSR      6
7           GND      5
8           DCD      1
20          DTR      4

 

So where the heck is Pin 1?

RJ45