Tacacs+ server dead issue

Question

Dear Cisco Guru's,
tacacs-server host 10.2.100.100
tacacs-server host 10.2.17.203
We have 2 tacacs+ servers defined in ACS 5.2. When putting 10.2.100.100 down, tacacs authentication continues to try to authenticate to the dead server,how is this possible ?
Normal behaviour should be going to the second (10.2.17.203) after the first Tacacs+ server timeout (default 5s).
Tacacs+ Server            : 10.2.100.100/49
              Socket opens:         15
             Socket closes:         15
             Socket aborts:          0
             Socket errors:          0
           Socket Timeouts:          0
   Failed Connect Attempts:         85
        Total Packets Sent:          0
        Total Packets Recv:          0
Tacacs+ Server            : 10.2.17.203/49
              Socket opens:        166
             Socket closes:        166
             Socket aborts:          0
             Socket errors:          0
           Socket Timeouts:          0
   Failed Connect Attempts:          0
        Total Packets Sent:        195
        Total Packets Recv:        195
Many thanks,
Lieven Stubbe
Belgian railways

Answer 1

Richard, Kashif,
1) 10.2.100.100 is a dummy IP to be sure we have a correct test scenario :
tacacs-server host 10.2.100.100
tacacs-server host 10.2.17.203
2) We have defined 2 testswitches with this config :
C3560 (12.2(53))
C3750 (12.2(55))
with our 3560, it hits the timeout counter of 5s of the dead tacacs server, once logged in, all other tacacs commands are treated by 10.2.17.203
Failed connect attemps raises by 1
with our 3750, with each tacacs command, it hits the timeout counter of 5s of the dead tacacs server everytime, before going to the 10.2.17.203, so all commands are executed but each time with a timeout delay of 5s.
Failed connect attemps raises by number of tacacs commands typed
Many thanks,
Lieven Stubbe
Belgian Railways