?Create OSPF area process ID 1
?default encap HDLC change to PPP
int? s0/0/0
encapsulation ppp? do for each end of serial link

?auth with CHAP each end of serial link
username? <router name on other end> password <cisco> on each end
int? s0/0/0
ppp authentication chap? on each end

?tunnelling at each end 
ip route 0.0.0.0 0.0.0.0? 10.1.1.2 default route to isp router on each router
interface tunnel? 0
ip address? 172.16.12.1 255.255.255.252
tunnel source? s0/0/0 
tunnel destination? 10.2.2.1

?ospf over tunnel each end adding networks that can travel over it
router ospf 1
network? 172.16.2.0 0.0.0.255 area 0

debug ppp negotiation
debug ppp packet
undebug all

show int tunnel 0
show ip route ospf
show ip int brief
show ip ospf int brief
show ip ospf neighbor
