Kerberos Client and Server on the same mashine

[Christian Kosmowski]

Hello,

Today i managed to set up an working kerberos Single Sign On 
Application. I spent hours on one problem regarding to getting a service 
ticket. I had both (a tomcat server) and the client (which was logged on 
to the domain) on one mashine. I just could'nt get a valid service ticket.

Now i found this thread here:

http://mailman.mit.edu/pipermail/kerberos/2003-November/004094.html

which says, that the client and the server must communicate through a 
real network interface.

To avoid this issue in future installation processes i need to find out:

- why they have to use a real interface (the more details the merrier)? 
Is this something on the encryption?
- how i can i force them talking through the a real interface?

thank you for any help!