Console Port on SG300-10 Switch Not Connecting

[Eli's Tech]

I recently bought a Cisco SG300-10 switch off eBay used. It is perfectly working, my laptop is plugged into it, with my router plugged into another port. It works completely fine. But, when I try to use a serial console connection on the console port on the back, I get error after error. I can't connect to the switch, no matter what I try. I've used PuTTY for most of the connection attempts, and it always says there is an error connecting. It says: Unable to open connection to /dev/ttyUSB0:   Unable to open serial port. No matter what settings I try, including all that Cisco have recommended using, it won't connect. I tried factory resetting the switch, but still no luck. I have no idea what the problem is. Any ideas? Also, this is the cable I'm using to connect: 

https://www.amazon.com/Adapter-Chipset-CableCreation-Converter-Register/dp/B0769DVQM1/ref=sr_1_3?crid=1TK70O1B1U01D&keywords=DB9+female+to+usb+adapter&qid=1649984462&sprefix=db9+female+to+usb+adapter%2Caps%2C194&sr=8-3

[luis_cordova]

Hi

Check the solutions in this link.

https://community.cisco.com/t5/small-business-switches/sg300-10-console-settings/td-p/2240249

Greetings

[Eli's Tech]

I already did. Nothing there really worked. Although, I didn't know what they meant by "blue-colored" and "standard 9-pin" cables. The end of my cable is blue. Is there a different cable I need to buy to connect to the switch correctly?

[Martin Aleksandrov]

Hi there,

You will need Cisco DB9 to RJ45 Console Cable. 

See the below guide for more detailed instructions:

https://www.cisco.com/c/en/us/support/docs/smb/switches/cisco-small-business-300-series-managed-switches/smb4984-access-the-cli-via-putty-using-a-console-connection-on-300-a.html

Here is what the cable looks like:

https://www.amazon.com/Console-Cable-Cisco-Router-Switch/dp/B005FTYR14

Thanks

[Eli's Tech]

The port on the back of the switch is already a DB9 port. Does that mean I need to plug the DB9 end of that cable into the switch, and then use a console to usb adapter or something?

[Manuka Rajapaksha]

First make sure that your USB to RS232 Adapter is functional.

I have seen some converters are not supporting to certain devices (Don't know the actual reason). 

Try with a Straight through console cable. Most desktop PCs have the DB9 port. 

https://www.amazon.com/StarTech-com-Straight-Through-Serial-Cable/dp/B000067SLX 

Or Else, use below

https://www.amazon.com/Serial-Ethernet-Adapter-Cable-2pcs-2-Cable/dp/B0811RHPLJ 

[Eli's Tech]

Well, my desktop does not have a DB9 port, so if I used the second adapter that you mentioned, would I plug the RJ45 jack into the ethernet port? Or would I get a console to usb adapter after the DB9 to RJ45 adapter?

[Manuka Rajapaksha]

Second adaptor is for just to convert the typical console cable (RJ45 to DB9) in to a straight through serial console. It is not using any Ethernet protocol. (similar to the first option). 

My assumption was, your DB9 to USB converter might not compatible with your switch or your PC. If you can try this activity with a diferent PC which has DB9 port, you can directly communicate through a serial connection without using any USB converter (which could be problematic sometimes).

Option 1: Use straight through console cable (first link) directly from the switch's serial port to PC without any "USB" converter.

Option 2: Use attached cable option (second link) with your RJ45 to DB9 console cable 

[Eli's Tech]

So, to make sure before I buy any more cables, I need to buy a DB9 to RJ45 adapter, then an RJ45 to USB adapter? Because the console port on the switch is a DB9 port. There is no RS232 port anywhere in the topology at all. Also, I have a laptop with linux, and a desktop with Windows 10, and both of them seemingly recognized the adapter. My windows PC showed its name in Device Manager, and I ran a command on my linux laptop and remember seeing it was completely recognized. (I don't remember the command, I had to look it up) So, I'm not sure if my cable is faulty, or the switch, or what the problem is.

[Manuka Rajapaksha]

RS232 is the definition of the interface. DB9 is the 9 pin connector which implement the RS232 connection.

Use one option from my last comment. I simply suggest you to skip the USB option from the scenario until you verify the switch's console port is working correctly. Sometimes, USB convertors can be seen in the device manager but not working propoerly because of the driver issues. 

Check this 3rd party article for more info:

https://www.rampfesthudson.com/is-rs-232-and-db9-the-same/#:~:text=What%20is%20RS232%20and%20DB9,a%2025%20pin%20connector%20also.  

[Eli's Tech]

Oh, sorry for the misunderstanding with the RS232 interface. I'm kind of new to the networking world, and all the experience I have is with virtual labs in Packet Tracer, where accessing the CLI of a switch is only a few clicks, and no challenge at all.

Anyway, what I'm trying to explain, is that there is no RJ45 anywhere. The console port, unlike most switches that I've seen before, is a DB9 RS232 port. There is no RJ45 console port on the switch. I have a DB9 RS232 to USB adapter, and I've plugged one end of that directly into the switch, with no adapters, and the other end directly into multiple of my computers, with no adapters. Either way, the device is recognized, but PuTTY will not display any output. So, do I need to get a DB9 to RJ45 cable, and then use an RJ45 to USB cable? Or something else?

I've included a picture of the console port and the labeling on the back of the switch, hope that helps!

[Manuka Rajapaksha]

No worries!!

Again,Use straight through serial cable (see the attached picture) without using any USB option first. 

Just read little bit about the DB9 serial connection. You'll know what to do.

I also attached DB9 gender convertor adaptor which might helpful to you.

[Eli's Tech]

The problem is that I don't have a DB9 port on my computer, which means I will need some sort of adapter to be able to plug into a computer to use PuTTY.