This document summarizes the cabling requirements for console and
auxiliary (AUX) ports. Cisco routers either have RJ-45-based or DB-25 DCE/DTE
console and AUX ports. You can connect either a terminal (DTE) or a modem (DCE)
to these ports. In either instance, you need both an RJ-45 cable and an
RJ-45-to-DB-25 or RJ-45-to-DB-9 connector.
In order to identify the RJ-45 cable type, hold the two ends of the
cable next to one another so you can see the colored wires inside the ends, as
There are three types of commonly used RJ-45 cabling: straight, cross
and rolled. Hold the two ends of an RJ-45 cable side by side. There are eight
colored strips, or pins, at each end. If the order of the colored pins is the
same at each end, the cable is straight. If the order of the colors is reversed
at each end, the cable is rolled.
Examine the sequence of colored wires to determine the type of RJ-45
cable. This section explains how you can do this.
This illustration shows serial cable CAB-R23= (part number 74-0173),
which is a general serial cable for all router platforms:
Both Ends of RS 232 Straight-through Cable for DB-25
This cable has a female DB-25 connector on one end and a male DB-25
connector on the other end. Either end of the CAB-R23 cable can be the Cisco
end or the network end, depending on whether the Cisco router is designated as
a DCE device or a DTE device. If the router is designated as a DCE device, the
female DB-25 connector is the Cisco end. If the router is designated as a DTE
device, the male DB-25 connector is the Cisco end.
Pin-outs for RS 232 Straight Through Cable
The first seven entries are DB-25 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.