RJ45 Wiring and Cables

DCE Device [Modem)

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Cisca DTE Device (Auk)

Cisca DTE Device (Auk)

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Straight RJ-45 Pins Rolled End and End

Connectors Signals Conn odors

© 2004 Cisco Systems, m

Cisco uses RJ-45 ports and connectors for console, auxiliary, and asynchronous port connections. The specific pinouts to be used on an RJ-45 interface for EIA-232 are not defined by any standards. Cisco defines the RJ-45 pinouts (shown in the figure) as DTE.

Cabling from the access server port (RJ-45) to an external device, such as a modem or terminal, requires the use of two cabling components:

■ RJ-45-to-RJ-45 cable: Can be either a rollover cable (reverse pins 1-8, 2-7, 3-6, 4-5) or a straight-through cable (1-1, 2-2, and so forth). To check whether a cable is straight-through or rolled, hold the two connectors (the two ends of the cable) side by side. With the keys at the back and the pins up, compare them by inspecting the color-coded wires inside the connector. If the wires use the same colors on the same pins, it is a straight-through cable. If the wires are a mirror image of each other, it is a rolled cable. The octal cable that is used to connect to the asynchronous ports is the equivalent of a rolled cable.

RJ-45-to-DB-25 adapter: Also straight-through or rolled.

— Male DTE (MDTE) or female DTE (FDTE) adapter. Straight-through.

— Male DCE (MDCE) or female DCE (FDCE) adapter. Rolled.

— MMOD (male modem-style) adapter. Rolled. This adapter supports only modems that are modified from MDCE connectors by wiring DB-25 pin 8 to DSR, instead of pin 6.

Working Connections

This topic describes how to connect devices to a Cisco router.

Working Connections

© 2004 Cisco Systems, Inc. All rights re

© 2004 Cisco Systems, Inc. All rights re

This figure displays the working connections between an access server and various types of end devices.

The auxiliary and console ports are configured as DTE devices on Cisco access servers. Terminals are also DTE devices. As noted earlier, two DTE devices cannot be directly connected unless the signals are rolled exactly one time. You must, therefore, roll the pins in either the cable or the DB-25 adapters, but not both. The "formula for success" is as follows:

■ DTE + rolled RJ-45 cable + straight DB-25 adapter + DTE = OK

■ DTE + straight RJ-45 cable + rolled DB-25 adapter + DTE = OK

When connecting a DTE to a DCE, however, you should have either no rolls or two rolls in the cable and the connector. The "formula for success" is as follows:

DTE + rolled RJ-45 cable + rolled DB-25 adapter + DCE = OK

DTE + straight RJ-45 cable + straight DB-25 adapter + DCE = OK

The part number for the rolled RJ-45-to-RJ-45 cable is CAB-500RJ.

When you order access servers with asynchronous ports, you must order the corresponding cable accessories. Order one CAB-OCTAL-KIT (an 8-lead octal cable and eight male DB-25 modem connectors) for each 68-pin asynchronous connector on the access server. If the modem uses an RJ-45 connector, order one CAB-OCTAL-ASYNC (a rolled 8-lead octal cable with RJ-45 connectors). Special adapters might be required.

Note Connecting a modem to the console port of a router is a security risk because it initially has no protection or security features enabled.

Cisco routers typically ship with a console and auxiliary port cabling kit that may include the following components:

■ RJ-45-to-DB-9 FDTE adapter (labeled TERMINAL)—primarily used to connect to a PC being used as a console terminal

■ RJ-45-to-DB-25 FDTE adapter (labeled TERMINAL)—can be used to connect a computer terminal or an older computer to the console or auxiliary port

■ RJ-45-to-DB-25 MDCE adapter (labeled MODEM)—used to connect the auxiliary port to a modem.

The table presents the port types for console and auxiliary ports on Cisco routers.

DB-25

RJ-45

Console port

DCE

DTE*

Auxiliary port

DTE

DTE

*DCE in the Cisco 1700 Series

*DCE in the Cisco 1700 Series

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