ipconfig will return information about the SERVER's NIC card...it would not have any information about the connecting users. that code might seem to work if your SQL server is also your development platform....if they are different, it would obviously not be accurate.

one of the data managment views (DMV) as the column sys.dm_exec_connections which is the connecting user's IP address; I'm not sure if you can use it in an logon audit trigger, I'd have to test that, but you can certainly use it inside a stored procedure or other statement after they've connected.

select

host_name(),

app_name(),

client_net_address

from sys.dm_exec_connections where session_id = @@spid