When a console cable ( usually a flat cable ) is connected from a Communication (COM) serial port of a PC to the router, and the correct configuration settings are applied to the Hyperterminal, a router prompt should appear on the screen after pressing the Enter key.
If the correct settings are not applied, the console port outputs garbage characters or no output at all. This makes the router appear as if it is hanging or not responding.
For more cabling information, refer to:
Cabling Guide for Console and AUX Ports
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To resolve this issue, perform these steps:
Step 1. Connect the console cable from the console port of the router to the COM port of the PC.
Open the Hyperterminal on the PC, select the correct COM port, and use these settings:
Speed: 9600 bps
Databits: 8
Parity bits: 0
Stop bit: 1
No flow control
For further instructions, refer to:
Applying Correct Terminal Emulator Settings for Console Connections
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Step 2. If this fails to solve the problem, swap cables or test the console cable.
This is done by attaching the console cable to the console port of another router.
Step 3. If the problem remains, the configuration register of the router may be set to a non-standard value for which the console connection speed is higher than 9600 bps.
If you can access the router through a Telnet session, check the value of the configuration register by issuing the show version command.
Ensure that it is set to 0x2102 or 0x102.
Reload the router for a configuration register change to take effect.
Change the configuration register by issuing the config-register command.
If the router has not been configured to accept a Telnet session, try different connection speeds.
These are valid connection speeds for Cisco routers:
1200 bps
2400 bps
4800 bps
9600 bps
19200 bps
38400 bps
57600 bps
115200 bps
Once you have gained access to the router, change the line speed to the default setting, as shown:
Router> enable Router#configure terminal Enter configuration commands, one per line. End with CNTL/Z. Router(config)#configure terminal Router(config)#config-register 0x2102 Router(config)#line con 0 Router(config-line)# speed 9600
Once you change the console speed, you lose connectivity.
Go to your terminal program, change the baud rate to 9600, and reconnect to the router console, as shown:
Router(config-line)#ctrl z Router #write memory Router #reload
If this method does not help for the Cisco 2600 and 3600 series platforms, refer to:
Cisco 2600 and 3600 Console Baud Reset Jumper
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of Cisco 2600 and 3600 Hints and Tricks web page
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Step 4. If in addition to not responding to the console, the router has stopped responding to queries sent from the network, such as Telnet or Simple Network Management Protocol (SNMP), refer to:
Troubleshooting Router Hangs
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Step 5. If none of these steps are helpful, there is a problem with the console port on the router.
To solve the problem, swap the router chassis.
Hope this helps.
Brad Reese
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