are there any OSPF tutorial that will explain how to implement OSPF in a medium-sized netowork?
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The closest thing i can think of off the top of my head is this site:
http://openmaniak.com/quagga_case2.php
Its not exactly for vyatta but we use quagga underneath and it sounds like you need the basics. It should be fairly easy to translate that config to ours.

If you need something more complex than those examples here is a 3 site openvpn tutorial with OSPF as the dynamic protocol from the same site. Again not exactly Vyatta but the configs are easy to translate.
http://openmaniak.com/openvpn_routing.php
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There's also a couple ospf class in vyatta university: http://www2.vyatta.com/store/Vyatta-University-Training-AM-EMEA
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Here you go:

http://www.impartlabs.com/2008/01/articles.html

a good ospf manual with samples based on Vyatta