RJ-48 and RJ-45

This is the most common of all interface standards. The two terms are very often confused - RJ45 is the physical male plug, and RJ48 is the electrical interface. Cisco's 2500 series routers all have RJ-48-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-48 cable and an RJ-48-to-DB25 connector.

NOTE: the RJ-45 is essentially identical to the RJ-48

Types of RJ-48 Cabling

There are two types of RJ-48 cabling, straight and rolled (crossover cable). If you hold the two ends of an RJ-48 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 it is a crossover cable. In the LAN arena, with Client-to-Hub connections, the straight version is used. For a cheap, 2-unit LAN, you can bypass the need for a Hub, and connect two PC's directly together using a crossover cable.

RJ-48 Port Pinouts

This chart shows the pinouts for RJ-48 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-48 Adapter Pinouts

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