Cisco Switch Console Port
In networking, the phrase “console” refers to the basic physical interface used for direct, out-of-band management and initial configuration, especially with relation to Cisco devices. When a device’s network connection is lost, a console provides a straightforward text-based interface used for initial setup and troubleshooting. Usually, a dedicated console cable is used to connect the device’s serial console port to a terminal program running on a different computer. Administrators can remotely control numerous network devices from a single point of access by using a console server, a device that combines several serial console ports.
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Function and Purpose
The console port, which offers local access to the Command-Line Interface (CLI), is an essential part of device management.
- Because console access is a direct physical connection that functions independently of the network interfaces (LAN/WAN), it is regarded as out-of-band management.
- Since network interfaces lack IP addresses and other information required for remote access, initial configuration is the main technique used to setup a device (router or switch) that has never been configured.
- Disaster recovery is crucial for conducting crucial maintenance activities like recovering passwords or loading a fresh IOS image using protocols like Xmodem, or for troubleshooting a device when remote network access (through Telnet or SSH) has failed.
- System Messages: By default, all unsolicited syslog messages, including debug output, are automatically copied to the console. The default logging console global command makes this possible.
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Cabling and Physical Ports
The physical port is a socket made to enable a cable connection between the network device and a computer running terminal emulator software.
| Connection Component | Description |
|---|---|
| Console Port Type | Traditionally an RJ-45 8-pin modular connector, often colored blue and labeled “Console”. Modern Cisco devices also frequently include a USB console port (e.g., mini-B USB port). |
| Console Cable | A rollover cable (or rolled cable) is required to connect a PC to the console port. |
| Rollover Pinout | Unlike straight-through or crossover cables, a rollover cable reverses the pin connections completely, connecting pin 1 to pin 8, pin 2 to pin 7, and so on. |
| PC Connection | The rollover cable connects the device’s console port (RJ-45) to the PC’s serial communication (COM) port (EIA-TIA 232 interface). This often requires an RJ-45-to-DB-9 or RJ-45-to-DB-25 converter plug. |
| USB Precedence | If a device has both RJ-45 and USB console ports connected simultaneously, the USB console connection supersedes the RJ-45 connection. |
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Standard Console Configurations
The terminal emulator needs to match the device’s default console port settings in order to create a session using terminal emulation software (like PuTTY or HyperTerminal). These configurations are commonly referred to as 9600 8N1.
The settings by default are:
- 9600 bits per second (bps) is the baud rate (speed). (Note: Up to 115,200 Kbps can be supported by more recent USB ports.)
- Eight bits make up the data.
- There is no parity.
- One stop bit is present.
- There is no hardware flow control or none at all.
Configuration Commands
The line configuration mode applies console port-specific configuration.
- Console Configuration Mode: Use the global command line console 0 to enter Console Configuration Mode.
- Set Password: The switch doesn’t ask for a console password by default. Use the password [value] command and then the login command to activate security.
- Prevent Input Disruption: Use the line subcommand logging synchronous to prevent obtrusive console messages (syslog messages or debug output) from interfering with instructions the user is inputting.
- Configure Session Timeout: The EXEC session timeout is set to 10 minutes by default. Use exec-timeout minutes [seconds] to modify this. The session won’t time out for lack of activity if you set it to exec-timeout 0 0.
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Console Port on Other Devices
Similar to the console port, the majority of Cisco routers also offer an auxiliary port, or “Aux port,” which is mostly used to connect to an external analogue modem so that remote, out-of-band CLI access can be accessed over the phone. Auxiliary ports are not commonly found on Cisco switches.
WLC Console Port: A console port for system recovery, out-of-band management, and initial boot operations is another feature of Wireless LAN Controllers (WLCs). The WLC console employs asynchronous connection settings by default, which include 8 data bits, 1 stop bit, and 9600 baud.