Thu May 26, 2011 8:49 pm
Generally speaking you want to use virtual links to join discontinuous backbone areas. Virtual links should only be used in emergencies, but a link failure would definitely count as that.
Unfortunately virtual links currently aren't working, so the Mikrotik recommended solution - for now, I guess, until virtual links work again - is to use an EoIP tunnel between the area 1 router that has L3 on it, and the area 0 router that has L1 and L2 on it. Then put the EoIP interface into area 0. At that point all traffic from area 1 will get to the backbone area via that tunnel if L1 fails.