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Sergio Arroyo

Tacacs do not function in Nexus 5000


For some reason, the tacacs not work on my nexus 5000.

This is the settings:

feature tacacs+

logging level tacacs 5

tacacs-server key 7 "clave"

ip tacacs source-interface Vlanx

tacacs-server host x.x.x.x                          >>> with this host works tacacs+

tacacs-server host x.x.x.x key 7 "clave"  >>> with this host does not work the tacacs+

aaa group server tacacs+ TACSERVER

    server x.x.x.x

    server x.x.x.x

    source-interface Vlanx


aaa authentication login default group TACSERVER

aaa authentication login error-enable

tacacs-server directed-request

These are the tests I've done to validate the configuration without success:

Nexus# test aaa server tacacs+ x.x.x.x user pass

error authenticating to server


Nexus# 2013 Aug  6 12:45:38 NITE4 %TACACS-3-TACACS_ERROR_MESSAGE: received bad authentication packet from x.x.x.x

NITE4# test aaa group TACSERVER user pass

user has failed authentication

The strange thing is that the other host is configured runs smoothly.

tacacs + the application is on a linux server has the following version:

tac_plus  version F5.0.0a1

The problem is very strange.

I need help.

Best regards

Sam Hertica
Cisco Employee

Hi Sergio,

It sounds like a shared secret mismatch between your server and the device. Since TACACS+ encrypts the entire packet, if the shared secret is off then each device recieves garble for their "communication"

I would check to make sure the shared secrets match. What could be the issue is the command

tacacs-server host x.x.x.x key 7 "clave" 

the 'key 7' bit indicates that a previously hashed password will be put here. I would use the

tacacs-server host x.x.x.x key 0 clave

If clave is your shared secret.

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