Breaking Telnet Attempt from IOS

Endorsed Question
Aug 1st, 2012

Hello all,

I have conducted research online for a solution to this issue but have not found one yet.

When attempting to telnet to an unresponsive address from a switch or router, the CLI shows "Trying x.x.x.x..." and eventually times out.  Example:

router#telnet 1.1.1.1

Trying 1.1.1.1 ...

% Connection timed out; remote host not responding

I am looking for the correct break sequence and/or terminal emulator settings that will cause the telnet session attempt to stop so that you do not have to wait for it to timeout.

My colleagues and I have unsuccessfully attempted the following break sequences using SecureCRT version 7 (with terminal emulation VT100) as well as with the Windows 7 Command Prompt:

  • ctrl + c
  • ctrl + c + c
  • ctrl + z
  • ctrl + z + z
  • ctrl + shift + 6
  • ctrl + shift + 6 + 6
  • ctrl + shift + 6 then x
  • ctrl + shift + 6 then x then x

We are able to successfully break out of traceroute and ping attempts using ctrl + shift + 6.

Does anyone know what break sequence and/or terminal emulation settings should be used to sucessfully break out of telnet session attempts?

Oscar

I have this problem too.
0 votes
Endorsed by Richard Burts
John Blakley about 1 year 8 months ago

I believe the ctrl+shift+6+x (CS6x) only works when you're consoled into the device and then telnetting from there. When you're telnetting from another telnet session, I don't believe this combination will work. You can alleviate some of the pain by changing your syn-wait time to 5. "ip tcp synwait-time 5"

If you want to change to ctrl-c, you can change your escape character to 3:

line vty 0 4

escape-character 3

HTH,

John

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John Blakley Thu, 08/02/2012 - 04:52

Im not familiar with securecrt but Ctrlshift6 is the correct break sequence. Try from a regular telnet session to see if it works. If so, there has to be a setting in securecrt that's doing something with your special key sequences.

Sent from Cisco Technical Support iPad App

Richard Burts Thu, 08/02/2012 - 05:37

I am familiar with SecureCRT and find it works quite well for me. I have used ctrl + shift + 6 and then x many times and have found that it works for me. I am puzzled why it is not working for Oscar.

HTH

Rick

ogomez2007 Thu, 08/02/2012 - 06:29

Thanks for replying.  As mentioned, we encounter this issue via the Windows Command Prompt as well (i.e. regular telnet session).  Also, it is not specific to a few devices.  We connect to different Cisco devices every day.

Richard, you mentioned ctrl + shift + 6 then x... this is the command that is used to return to the original session when you have a nested telnet session to another device.  This works fine for us.  What does not function is trying to cancel a telnet session when it is "trying" to connect.  We are forced to wait for the telnet attempt to timeout... not the end of the world, but very annoying.  Can you verify that you are able to cancel a telnet attempt with "ctrl + shift + 6 then x"?

John Blakley Thu, 08/02/2012 - 07:27

I believe the ctrl+shift+6+x (CS6x) only works when you're consoled into the device and then telnetting from there. When you're telnetting from another telnet session, I don't believe this combination will work. You can alleviate some of the pain by changing your syn-wait time to 5. "ip tcp synwait-time 5"

If you want to change to ctrl-c, you can change your escape character to 3:

line vty 0 4

escape-character 3

HTH,

John

Richard Burts Thu, 08/02/2012 - 14:43

I was obviously a bit too quick to respond and for that I apologize. I was reacting to the suggestion that SecureCRT was not doing somethign as it should with the ctrl + shift + 6. When I read a bit more carefully I realize that John very carefully and correctly phrased it in terms of try it from some other environment and if it works there (which it does not) then it points to some issue with SecureCRT.

I agree that there does not seem to be a way to cancel a telnet attempt that is "trying". And I endorse his suggestion that changing the synwait time is a way to reduce the pain.

HTH

Rick

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Posted August 1, 2012 at 8:25 AM
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