OSPF Sham-Links

Pretty cool article that explains and shows how the sham link works. Important point here that I have not picked up from any vendors workbook - the Sham Links makes they MPLS transported routes appear as intra-area (instead of the default inter-area) and thus the reason why you can now tweak the ospf costs between your MPLS link and your backup link.

http://blog.ipexpert.com/2010/06/14/ospf-sham-links/