01-27-2025 10:55 AM
I have a Cisco router 2900 with a Cisco HWIC-16A 16 port Async interface card on the back that i plan to use to console into nearby switches in case they lose connectivity for an OOB solution.
I have tried many documentation regarding this setup and I cannot get this to work. What is the proper configuration for the ASYNC interfaces and what the command I need to use to console into those switches from my router?
02-12-2025 11:20 AM
Ok. Can you share the configuration of the con 0 lien from your switch which you are trying to access via the terminal server?
Why are you saying that "the switches are set up to only accept SSH". If you are referring at the configuration
line vty 0 4
transport input ssh
found on the switch, I can tell you that it doesn't apply because you are trying to access the switch on the console line which shouldn't have the transport input ssh command and even if it did it wouldn't deny access to the console line.
You can convince yourself that this is true by trying to connect your PC, using a Cisco serial console cable, to the console of your switch. Use what terminal program you like, set the connection method to serial, choose the correct COM port from your PC, set the connection parameters to 9600, 8, N, 1 and see if you can connect.
If your connection is successful, then also the connection via the terminal server should be successful, unless you connected something wrong.
02-12-2025 01:14 PM
02-12-2025 03:05 PM
I'm glad to hear that the solution is working out for you.
01-29-2025 04:37 PM
@raijin199 wrote:I have a Cisco router 2900 with a Cisco HWIC-16A 16 port Async interface card on the back that i plan to use to console into nearby switches in case they lose connectivity for an OOB solution.
I have tried many documentation regarding this setup and I cannot get this to work. What is the proper configuration for the ASYNC interfaces and what the command I need to use to console into those switches from my router?
You first need to set up the async interfaces on the router. Access the router’s global configuration mode and configure each async interface (for example, Async0/0/0 to Async0/0/15) with the following settings: disable IP addressing, set the encapsulation to slip, and configure the stopbits to 1. Once this is done, configure the line settings for the async ports. Enter line configuration mode for the lines corresponding to the async interfaces and apply the transport input all, transport output all, no exec, and stopbits 1 settings. The line numbers typically start from 33, but this can vary based on your specific router configuration. Use the show line command to verify the line numbers.
Next, create a loopback interface, which is used for reverse Telnet connections. Assign it an IP address, such as 192.168.1.1 with a subnet mask of 255.255.255.255. For reverse Telnet functionality, assign a rotary group to the lines with the command rotary 1. This setup allows access to the async interfaces via Telnet by connecting to the loopback address and using ports calculated as 2000 + line number. For example, to access line 33, you would use telnet 192.168.1.1 2033. Ensure that you physically connect the async ports on the router to the console ports of the switches using appropriate cables and verify that the baud rate and serial settings match the connected devices' requirements.
01-29-2025 11:58 PM
@antisocial11224 , you don't need the rotary command on the async lines because the functionality to access it with port number 2000 + async line number exists even without the rotary command configured on it.
The rotary command enables a new range of ports on the router - 3000+rotary number and you can approach the terminal server configuration a little different.
Using the rotary option in IOS you can controls the vty line you connect to the router:
line vty 1
rotary 1
In our example, if you telnet/ssh on port 3001 you will land on vty 1 which is configured with rotary 1.
Now to have a certain vty connect with a specific async line, you can use the "autocommand" command on the vty line:
line vty 1
rotary 1
autocommand telnet 10.10.10.99 2003
Hope this helps.
01-30-2025 03:43 AM
@liviu.gheorghe Thank u for correcting me
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