I have been flying though some of the labs and the experience is really humbling there is tonnes of stuff that I have never configured before and it takes me a little bit of time to get used to. One of these items is dot1x authentication so below is a brief command reference/primer for the commands.

Right first off we need to enable the aaa new model

DistSwitch(config)#aaa new-model

Then we need to configure dot1x to be used for authentication and as dot1x uses radius define the radius server, pretty standard stuff

DistSwitch(config)#aaa authentication dot1x default group radius
DistSwitch(config)#radius-server host 10.10.10.100 key secretkey

To prevent bad things from happening such as locking yourself out use the following command to only use local login for the lines

DistSwitch(config)#aaa authentication login default line

Now for the interface configuration, to use dot1x the ports must be access ports so lets sort that out

interface FastEthernet0/1
 switchport mode access

This is the most important command and specifies that the port should be either force-authorised where the port is always allowed on the network, force-unauthorised where the port is never allowed on the network, and finally auto where the port is either authorised if dot1x authentication succeeds or unauthorised if it doesnt.

DistSwitch(config-if)#dot1x port-control ?
  auto                PortState will be set to AUTO
  force-authorized    PortState set to Authorized
  force-unauthorized  PortState will be set to UnAuthorized

Still on the interface there are are a couple more useful commands, the next command puts the port into the specified vlan if authentication fails

DistSwitch(config-if)#dot1x auth-fail vlan 666

And this command puts the port in the specified vlan if the connected host does not support dot1x, handy for guests

DistSwitch(config-if)#dot1x guest-vlan 90

And always there is a couple of show commands that we need to do to check that everything is working correctly. To check the queries and responses sent to each radius server just use;

DistSwitch#show aaa servers

RADIUS: id 1, priority 1, host 10.10.10.100, auth-port 1645, acct-port 1646
     State: current UP, duration 1743s, previous duration 0s
     Dead: total time 0s, count 0
     Quarantined: No
     Authen: request 0, timeouts 0
             Response: unexpected 0, server error 0, incorrect 0, time 0ms
             Transaction: success 0, failure 0
     Author: request 0, timeouts 0
             Response: unexpected 0, server error 0, incorrect 0, time 0ms
             Transaction: success 0, failure 0
     Account: request 0, timeouts 0
             Response: unexpected 0, server error 0, incorrect 0, time 0ms
             Transaction: success 0, failure 0
     Elapsed time since counters last cleared: 12m

And to see the dot1x interface specific information the following command provides that information

DistSwitch#show dot1x interface fa0/1
Dot1x Info for FastEthernet0/1
-----------------------------------
PAE                       = AUTHENTICATOR
PortControl               = AUTO
ControlDirection          = Both
HostMode                  = SINGLE_HOST
Violation Mode            = PROTECT
ReAuthentication          = Disabled
QuietPeriod               = 60
ServerTimeout             = 0
SuppTimeout               = 30
ReAuthPeriod              = 3600 (Locally configured)
ReAuthMax                 = 2
MaxReq                    = 2
TxPeriod                  = 30
RateLimitPeriod           = 0
Auth-Fail-Vlan            = 666
Auth-Fail-Max-attempts    = 3
Guest-Vlan                = 90