Not able to telnet

[Tabish Hussain]

Hi Team,

I recently upgraded firmware of Switch(C9200L). But after upgradation I can only telnet the device via putty and not on Windows.

Before upgradation I could telnet using windows as well. Also, I can still telnet from my windows to devices that are not upgraded.

Any solution?

[Flavio Miranda]

Hi

 From which version to which version?  Sounds to be like some more advanced security feature present on this new version.

Actually you should not use telnet anymore but SSH.  I would say that Putty may use an telnet implementation that is accepted by this new cisco code while windows does not. 

 But, a good advide. Start using SSH instead.

[Tabish Hussain]

I updated SW C9200L-48T-4X from version 16.9.5 to 17.6.5.

Also now after upgrade I am not even able to telnet via putty also.

Any solutions before trying SSH?

Thanks!

[Richard Burts]

When you attempt to telnet are there any entries in the logging on the switch about the event? Perhaps that might shed some light on the issue. Also the suggestion about trying debug might provide helpful information.

[Rich R]

Agreed with @Flavio Miranda you should only be using SSH.
But if you want to know why telnet isn't working get a packet capture on the windows PC and run a "debug telnet" on the switch while trying to connect.

[Omer Waheed]

Hi Tabish,

Try to add command "enable secret" in your switch.

Regards