S5700 Telnet Failed

Latest reply: Mar 19, 2014 03:24:31 3479 3 0 0

Recently received two new switches, model S5700-52P-LI-AC (V200R001C00), I've tried configure the authentication-mode password user the user-interface vty.

However , the telnet fail but telnet will be successful if the authentication mode is aaa.

Below are the config:


user-interface con 0
 user-interface vty 0 4
  authentication-mode password
 user privilege level 1
user-interface vty 16 20


While debugging vty negotiate, the error "EXEC do not support null authentication-mode".

Is there any issue with this switch or my configuration have problem?

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Created Mar 12, 2014 08:47:17 Helpful(0) Helpful(0)



There have been several changes to the authentication on these devices in recent versions, from the example you have given it seems to me that you need to add the "set authentication password cipher mypassword" command to enable the authentication fully. The "null" in the debug is indicating you have set the authentication to use password but not set a password.


Regards Nigel


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Created Mar 12, 2014 08:55:40 Helpful(0) Helpful(0)

Hi Nigel,

I did type in the command "set authentication password cipher mypassword".

But after typing, the command don't appear in the current-configuration.

I have even tried "set authentication password" <enter> "mypassword".

Same result as above.

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Created Mar 19, 2014 03:24:31 Helpful(0) Helpful(0)

Hi all,

Problem solved.

I just realise it's due to the password length.

No error message when I key in password length which exceeded the 56 characters.

When I change to a shorter password, the authentication works.

But still don't understand why the cipher encryption in AAA could accept the same password.

Might be possible that AAA cipher encryption type differs from the user-interface cipher encryption type?

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