Hi all,I'm configuring a Network Access Control Solution (Packetfence ) but i have a problem to authenticate my users.I hope that someone will be able to help me.-I have a windows 2008 Active Directory for my users -I'm using a cisco 2950 switch to authenticate my users but when connecting a host i get this error on my switch,It seems like the switch cannot reach the server but i'm sure that the radius server ip address is 192.168.10.1 : RADIUS: Retransmit id 4 00:28:11: RADIUS: Retransmit id 4 00:28:13: RADIUS: Retransmit id 4 00:28:15: RADIUS: Marking server 192.168.10.1:1812,1813 dead 00:28:15: RADIUS: Tried all servers. 00:28:15: RADIUS: No valid server found. Trying any viable server 00:28:15: RADIUS: Tried all servers. 00:28:15: RADIUS: No response for id 4 00:28:15: AAA/AUTHEN (3539210218): status = ERROR 00:28:15: AAA/AUTHEN/START (3539210218): no methods left to try 00:28:15: AAA/AUTHEN (3539210218): status = ERROR 00:28:15: AAA/AUTHEN/START (3539210218): failed to authenticate 00:28:15: AAA/MEMORY: free_user_quiet (0x80D4E810) user='Prof-PC\Prof' ruser='Prof-PC\Prof'  port='FastEthernet0/2' rem_addr='00-40-D0-67-D0-B1/00-18-BA-9B-E7-82' authen_type=6 service=17 priv=1 This is my swicth configuration here  :  Building configuration... Current configuration : 2480 bytes!version 12.1no service pad service timestamps debug uptime service timestamps log uptime no service password-encryption!hostname Switch!aaa new-modelaaa group server radius packetfence  server 192.168.10.1 auth-port 1812 acct-port 1813!aaa authentication login default local aaa authentication dot1x default group packetfence aaa authorization network default group packetfence!username admin password 0 thegame ip subnet-zero!!spanning-tree mode pvst no spanning-tree optimize bpdu transmission spanning-tree extend system-id dot1x system-auth-control!!!!interface FastEthernet0/1  switchport trunk native vlan 10  switchport trunk allowed vlan 1,10,20,30,40,60,100  switchport mode trunk !interface FastEthernet0/2  switchport access vlan 4  switchport mode access  dot1x port-control auto  dot1x host-mode multi-host  dot1x reauthentication  spanning-tree portfast!interface FastEthernet0/3!interface FastEthernet0/4!interface FastEthernet0/5!interface FastEthernet0/6!interface FastEthernet0/7!interface FastEthernet0/8!interface FastEthernet0/9!interface FastEthernet0/10!interface FastEthernet0/11!interface FastEthernet0/12!interface FastEthernet0/13!interface FastEthernet0/14!interface FastEthernet0/15!interface FastEthernet0/16!interface FastEthernet0/17!interface FastEthernet0/18!interface FastEthernet0/19!interface FastEthernet0/20!interface FastEthernet0/21!interface FastEthernet0/22!interface FastEthernet0/23!interface FastEthernet0/24!interface Vlan1 no ip address no ip route-cache shutdown!interface Vlan4 ip address 192.168.4.1 255.255.255.0 no ip route-cache shutdown!interface Vlan10 ip address 192.168.1.5 255.255.255.0 ip helper-address 192.168.10.1 no ip route-cache!interface Vlan20 ip address 192.168.20.1 255.255.255.0 no ip route-cache shutdown!interface Vlan30 ip address 192.168.30.1 255.255.255.0 no ip route-cache shutdown!interface Vlan40 ip address 192.168.40.1 255.255.255.0 no ip route-cache shutdown!interface Vlan50 no ip address no ip route-cache shutdown!interface Vlan60 ip address 192.168.60.1 255.255.255.0 no ip route-cache shutdown!interface Vlan100 ip address 192.168.100.1 255.255.255.0 no ip route-cache shutdown! ip http server radius-server host 192.168.10.1 auth-port 1812 acct-port 1813 timeout 2 key thegame radius-server retransmit 3 radius-server vsa send authentication!line con 0line vty 5 15!!end