Lessons · Network switches · the port that asks who you are
The configuration arrives; the identity does not
802.1X makes the port carry nothing until the device proves who it is. The port-level lines restore like any others. What the authentication server knows about the OLD switch does not.
Hone is a place to practise programming. This is one of its lessons, written out in full and free to read without an account.
What it is for
It is the same shape as the SSH key. A shared secret and a place on somebody's list of known switches are not in your backup, and they are not yours to add.
How to think about it
Before the swap, tell whoever runs that server the box is changing. It is the one part of the job that cannot be done from the console.
Worked example
enableIn.
configure terminalConfiguring.
interface gi0/8A meeting room socket.
switchport mode accessOrdinary so far.
switchport access vlan 10And a VLAN, in case the server does not choose one.
authentication port-control autoReal IOS, and this practice switch says so rather than pretending.
dot1x pae authenticatorThe same. Neither line is invented; neither is simulated here.
endDone.
show running-config | section GigabitEthernet0/8What you can see is the ordinary half. The half that matters lives on somebody else's server.
Your turn
Show this one interface's block of the configuration.
show running-config | GigabitEthernet0/8
Console into a switch
The trap
Assuming a port that authenticates elsewhere will authenticate here because the configuration matches. The configuration was never the part in question.