Thursday, October 27, 2016

CMD Windows Telnet Not Recognzied As Internal External Command

When you try to run telnet from a command prompt, it says 'telnet is not recognized as an internal or external command'.

If you're in a hurry to get this resolved: chances are you have this problem because you're trying to run telnet.exe from a 32bit version of cmd; or you haven't enabled telnet from the Add/Remove Windows Features in Control Panel. I'm going to focus on the first case.

Telnet (among other programs) can only be run from cmd when cmd is running in 64bit mode. You can start cmd in 64bit mode by doing a search (Window+Q, Window+R, or possibly Window+S). If you're using another program to start cmd or telnet, you need to make sure the program you run cmd or telnet from is 64bit.

I recently ran across a situation where I needed to use the Windows telnet client. As of right now, I'm using Windows 10. To make a long story short, the device I was trying to connect to didn't like Putty's telnet client, and it was causing issues.

Windows Telnet to the rescue... or so I thought. I already had the client installed, but for some reason when I ran telnet from cmd, it was saying that telnet is not recognized as an internal or external command.

When I did a directory listing inside of C:\windows\system32 from cmd, it wouldn't even list telnet.exe, even though I could see it in the windows explorer gui.

Every once in a while, I could get the telnet program to execute. After some troubleshooting, I realized that the only time it would run is when the cmd program was running in 64bit mode.

Now, my particular situation was that I was trying to run the telnet client via Bayden's Slickrun program (which is an excellent launcher program that you should check out). Sure enough, I had installed the 32bit version of SlickRun, not 64bit. So, when I was trying to run cmd or telnet from SlickRun, it was opening the 32bit version of cmd and erroring out.

If cmd is executed from a 64bit program, it'll run cmd in 64bit mode, otherwise it runs in 32bit mode...and you can't execute a lot of commands...including telnet.exe

In my case, I simply downloaded the 64bit version of SlickRun.

Hopefully this puts you on the right path to getting this resolved!