X.25 problem

I've some problem while setting up my X.25 ver 9.2.
Can someone out there shed a light on the following?

1. ) How to check and ensure that the physical layer
is
OK?
2. ) How to confirm that the data layer is working
well?
3. ) How to confirm that the network layer is OK?

4. ) Any good website or documents that I can
reference?

I'm getting the following error during startup...

# /etc/init.d/x25.control start
Starting the X.25 software - please wait
X.25 : Creating link 1...
X.25 : unable to identify PPA associated with LLC2
X.25 : Can't create level 2 for link 1
X.25 : link 1 has been stopped

What is this error means and what could be the
problem?

TIA.

Regards,
Andrew
Yahoo! - Official partner of 2002 FIFA World Cup
http://fifaworldcup.yahoo.com

[915 byte] By [CodeProf.com] at [2007-12-24 22:49:00]