3750 switch that is booting up with weird characters and never gets fully booted

[jamierask55]

I am attaching a file that shows the garbage that comes up on a 3750 switch when I try to boot it up. It worked fine for about 3 months after I bought it but I tried to attach my other 3750 switch to stack them and I believe something happened to make the one switch unusable at this time. I need to know how to get the IOS loaded back onto the switch or a back door through maybe the aux port to get something done to make this thing work again. It wasn't cheap but that's the chance you take buying something from ebay. It worked fine for several months and then I took a break for about 2 months with medical issues and when I started back up again I got the garbage. Anything anyone can help with would be greatly appreciated.

Thanks,

Jamie

[Antonio Knox · Accepted solution]

I'd recommend first checking your serial connection settings (try putty if you haven't already). Some baud rates to try:

4800

9600

19200

38400

76800

115200

 Secondly, consider replace your console cable if option 1 doesn't work.

[jamierask55]

I have tried a lower baud rate but will try the higher rate to see if that works. I am using tera term and the cable works for the access server stack so I am fairly confident that the cable is not the problem. I am using a serial to usb converter but that works with all the other devices I have as well. The cable works on the other 3750 48 port poe switch so I just do not think that increasing the baud rate is going to do the trick but I will certainly give it a try. The whole issue is that it worked for about 3 months and I just do not know if trying to stack the two switches together had some effect on the one that is giving me all the garbage using tera term.

[Richard Burts · Accepted solution]

Jamie

The kind of garbage/jiberish while booting is a frequent symptom of a mismatch between the speed of the console and the speed of your terminal emulator. I believe that Antonio in on the right track in suggesting that you try various speeds in your terminal emulator, but I am surprised that the list of speeds did not include 1200 and 2400.

The title in this thread indicates that the switch does not get fully booted. Are you saying this based only on the failure to get console messages or are there other symptoms that indicate that the switch did not complete its boot sequence? I have experienced situations where the device did boot and did pass traffic but could not access via its console and I wonder if that might be the situation here. And if it is then perhaps telnet/SSH to its management address might provide the ability to further troubleshoot this issue.

Also if the switches are stacked I wonder what is the result if you attempt console access via the other switch.

HTH

Rick

[jamierask55]

Rick,

I got the switch to respond by changing my baud rate to 115200 in tera term and then changed the switch back to default master instead of the 8th switch that was in a stack bought from ebay. I also read that if I went in line con 0 mode and changed the speed of the console port back to 9600 that it would work. I changed it and it did work however after doing a write command and connecting the access server back to the switch it stopped working again. You might have something in stacking them as I bought 2 stack cables to go with my 2 3750 switches thinking I might play around with that in my lab. Maybe using the one switch that works with the access server and connecting the other one by stack cables I might be able to get into the client switch through the master. I read up on the 3750 as one switch ports were 4/0/1 and the other was 8/0/1 so I learned alot about these switches by reading cisco docs and finding out how to change them back to 1/0/1 so they are back to default. Good learning experience and it pays to use google to get appropriate cisco docs to work through things. I am just curious about the speed of that console port and why it wouldn't work even after changing the speed back to 9600 in line con mode and doing a save. I changed the tera term back to 9600 and that works as long as I am directly plugged into that switches console port. I just want it to work through my access server now so I can control the whole lab stack with access server commands. Any ideas what might be keeping the access server connection from working at 9600 baud rate?

Thanks for your time and have a great day.

Jamie

[Richard Burts]

Jamie

Thanks for the update. And thanks for using the rating system to mark this question as answered. I am glad that this has been a good learning experience and that you now understand more about these switches. I am not sure why the connection through the access server is not work but it sounds like there may be some speed setting in the access server. What kind of access server is this and how is it configured?

HTH

Rick

[jamierask55]

I have been able to get into my 3750 switch changing the baud rate to 115,200 on my tera term console connection settings. I changed that stack back to master on both my switches but may connect them together with a stack cable(2) and manage them from one switch. I have another problem and that is getting my access server to work with that switch. I plug directly into the console port and it works on the higher setting. I went into line config mode and changed that speed back to 9600 and then changed the baud rate on tera term and presto it works, but as soon as I plug an octocable RJ45 cable into the console port and try to manage the switch it fails and I have to go back to directly connecting to the switch again to get it to work. Maybe if I stack them and use the other switch as the master then it would work but if I use them separately it would be nice to use the access server to switch between all of my lab routers and switches. I did a write as well to save the speed config change. Any thoughts on how to get this to work without any more problems? I read someplace that I might have to get the switch into Rom Mon mode to make this speed change but I do not know why it worked for me when I was directly plugged in with the console cable and then stops working when trying to connect with the access server. Thanks for all your help so far it was great to see the the switch responding to commands again. 

Jamie

[abdullahnoori]

Yes, It is because of the speed. I changed it to a different speed and it worked... As soon as you change the speed, you will not be able to access the switch, so you have to log back in to switch to the speed that you have changed it and save the configuration...