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Cabling the Console Connection

The physical console connection, both old and new, uses three main components: the physical
console port on the switch, a physical serial port on the PC, and a cable that works with
the console and serial ports. However, the physical cabling details have changed slowly
over time, mainly because of advances and changes with serial interfaces on PC hardware.
For this next topic, the text looks at three cases: newer connectors on both the PC and the
switch, older connectors on both, and a third case with the newer (USB) connector on the
PC but with an older connector on the switch.

More modern PC and switch hardware use a familiar standard USB cable for the console
connection. Cisco has been including USB ports as console ports in newer routers and
switches as well. All you have to do is look at the switch to make sure you have the correct
style of USB cable end to match the USB console port. In the simplest form, you can
use any USB port on the PC, with a USB cable, connected to the USB console port on the
switch or router, as shown on the far right side of Figure 6-3.
Free CISCO CCNA Routing and Switching ICND1 Study Guide
Figure 6-3 Console Connection to a Switch

Older console connections use a PC serial port that pre-dates USB, a UTP cable, and an
RJ-45 console port on the switch, as shown on the left side of Figure 6-3. The PC serial port
typically has a D-shell connector (roughly rectangular) with nine pins (often called a DB-9).
The console port looks like any Ethernet RJ-45 port (but is typically colored in blue and
with the word “console” beside it on the switch).

The cabling for this older-style console connection can be simple or require some effort,
depending on what cable you use. You can use the purpose-built console cable that ships
with new Cisco switches and routers and not think about the details. However, you can
make your own cable with a standard serial cable (with a connector that matches the PC), a
standard RJ-45 to DB-9 converter plug, and a UTP cable. However, the UTP cable does not
use the same pinouts as Ethernet; instead, the cable uses rollover cable pinouts rather than
any of the standard Ethernet cabling pinouts. The rollover pinout uses eight wires, rolling
the wire at pin 1 to pin 8, pin 2 to pin 7, pin 3 to pin 6, and so on.

As it turns out, USB ports became common on PCs before Cisco began commonly using
USB for its console ports. So, you also have to be ready to use a PC that has only a USB port
and not an old serial port, but a router or switch that has the older RJ-45 console port (and
no USB console port). The center of Figure 6-3 shows that case. To connect such a PC to
a router or switch console, you need a USB converter that converts from the older console
cable to a USB connector, and a rollover UTP cable, as shown in the middle of Figure 6-3.

NOTE When using the USB options, you typically also need to install a software driver
so that your PC’s OS knows that the device on the other end of the USB connection is the
console of a Cisco device. Also, you can easily find photos of these cables and components
online, with searches like “cisco console cable,” “cisco usb console cable,” or “console cable
converter.”

The newer 2960-X series, for instance, supports both the older RJ-45 console port and a
USB console port. Figure 6-4 points to the two console ports; you would use only one or
the other. Note that the USB console port uses a mini-B port rather than the more commonly
seen rectangular standard USB port.

Free CISCO CCNA Routing and Switching ICND1 Study Guide
Figure 6-4 A Part of a 2960-X Switch with Console Ports Shown

After the PC is physically connected to the console port, a terminal emulator software
package must be installed and configured on the PC. The terminal emulator software treats
all data as text. It accepts the text typed by the user and sends it over the console connection
to the switch. Similarly, any bits coming into the PC over the console connection are
displayed as text for the user to read.

The emulator must be configured to use the PC’s serial port to match the settings on the
switch’s console port settings. The default console port settings on a switch are as follows.
Note that the last three parameters are referred to collectively as 8N1:
■ 9600 bits/second
■ No hardware flow control
■ 8-bit ASCII
■ No parity bits
■ 1 stop bit

Figure 6-5 shows one such terminal emulator. The image shows the window created by the
emulator software in the background, with some output of a show command. The foreground,
in the upper left, shows a settings window that lists the default console settings as
listed just before this paragraph.

Free CISCO CCNA Routing and Switching ICND1 Study Guide
Figure 6-5 Terminal Settings for Console Access

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