Well, in fact my network is almost complex. Here is the complete scenario and exact problems I have:
HQ - (PPTP over Intranet) - HAS - (Wireless Link) - K1 - (PPTP over Intranet) - K2
And also:
HQ - (PPTP over Intranet) - K1Backup - (Cable) - K1
HQ - (PPTP over Intranet) - K2Backup - (Cable) - K2
K1Backup and K2Backups are connected through LTE for failover connecting to HQ.
Subnets:
HQ: 192.168.134.0/24
K1: 192.168.125.0/25
K2: 192.168.179.0/25
OSPF Configurations:
HQ:
/routing ospf area
add area-id=0.0.0.1 name=HQ-HAS-Transit
add area-id=0.0.0.5 name=K1-HQ-Transit
add area-id=0.0.0.7 name=K2-HQ-Transit
/routing ospf instance
set [ find default=yes ] metric-connected=1 metric-static=10 redistribute-connected=as-type-1 redistribute-static=as-type-1 router-id=172.15.0.1
/routing ospf interface
add cost=100 interface=K1 network-type=point-to-point
add cost=100 interface=K2 network-type=point-to-point
/routing ospf network
add area=backbone network=192.168.0.0/16
add area=backbone network=172.16.0.0/12
add area=HQ-HAS-Transit network=172.16.2.4/30
add area=K1-HQ-Transit network=10.0.0.0/30
add area=K2-HQ-Transit network=10.0.0.4/30
/routing ospf virtual-link
add neighbor-id=172.15.0.2 transit-area=HQ-HAS-Transit
add disabled=yes neighbor-id=172.15.0.5 transit-area=K1-HQ-Transit
add disabled=yes neighbor-id=172.15.0.6 transit-area=K2-HQ-Transit
HAS:
/routing ospf area
add area-id=0.0.0.1 name=HQ-HAS-Transit
add area-id=0.0.0.2 name=HAS-K1-Transit
/routing ospf instance
set [ find default=yes ] metric-connected=1 metric-static=10 redistribute-connected=as-type-1 redistribute-static=as-type-1 router-id=172.15.0.2
/routing ospf network
add area=backbone network=172.27.2.0/24
add area=HAS-K1-Transit network=172.27.3.0/24
add area=backbone network=172.27.5.0/24
add area=HQ-HAS-Transit network=172.16.2.4/30
/routing ospf virtual-link
add neighbor-id=172.15.0.1 transit-area=HQ-HAS-Transit
add neighbor-id=172.15.0.3 transit-area=HAS-K1-Transit
K1:
/routing ospf area
add area-id=0.0.0.2 name=HAS-K1-Transit
add area-id=0.0.0.3 name=K1-K2-Transit
add area-id=0.0.0.4 name=K1-Backup-Transit
/routing ospf instance
set [ find default=yes ] metric-connected=1 metric-static=10 redistribute-connected=as-type-1 redistribute-static=as-type-1 router-id=172.15.0.3
/routing ospf network
add area=backbone network=192.168.125.0/25
add area=backbone network=172.19.0.0/24
add area=backbone network=172.20.0.0/24
add area=HAS-K1-Transit network=172.27.3.0/24
add area=K1-K2-Transit network=172.16.9.0/30
add area=K1-Backup-Transit network=172.16.5.0/30
/routing ospf virtual-link
add neighbor-id=172.15.0.2 transit-area=HAS-K1-Transit
add neighbor-id=172.15.0.4 transit-area=K1-K2-Transit
add neighbor-id=172.15.0.5 transit-area=K1-Backup-Transit
K2:
/routing ospf area
add area-id=0.0.0.3 name=K1-K2-Transit
add area-id=0.0.0.6 name=K2-Backup-Transit
/routing ospf instance
set [ find default=yes ] metric-connected=1 metric-static=10 redistribute-connected=as-type-1 redistribute-static=as-type-1 router-id=172.15.0.4
/routing ospf network
add area=backbone network=172.21.0.0/24
add area=backbone network=192.168.179.0/25
add area=K1-K2-Transit network=172.16.9.0/30
add area=K2-Backup-Transit network=172.16.6.0/30
/routing ospf virtual-link
add neighbor-id=172.15.0.3 transit-area=K1-K2-Transit
add neighbor-id=172.15.0.6 transit-area=K2-Backup-Transit
K1Backup:
/routing ospf area
add area-id=0.0.0.4 name=K1-Backup-Transit
add area-id=0.0.0.5 name=K1-HQ-Transit
/routing ospf instance
set [ find default=yes ] metric-connected=1 metric-static=10 redistribute-connected=as-type-1 redistribute-static=as-type-1 router-id=172.15.0.5
/routing ospf interface
add cost=80 interface=HQ network-type=point-to-point
/routing ospf network
add area=K1-Backup-Transit network=172.16.5.0/30
add area=K1-HQ-Transit network=10.0.0.0/30
/routing ospf virtual-link
add neighbor-id=172.15.0.3 transit-area=K1-Backup-Transit
K2Backup:
/routing ospf area
add area-id=0.0.0.6 name=K2-Backup-Transit
add area-id=0.0.0.7 name=K2-HQ-Transit
/routing ospf instance
set [ find default=yes ] metric-connected=1 metric-static=10 redistribute-connected=as-type-1 redistribute-static=as-type-1 router-id=172.15.0.6
/routing ospf interface
add cost=100 interface=HQ network-type=point-to-point
/routing ospf network
add area=K2-Backup-Transit network=172.16.6.0/30
add area=K2-HQ-Transit network=10.0.0.4/30
/routing ospf virtual-link
add neighbor-id=172.15.0.4 transit-area=K2-Backup-Transit
Now, this is the problem: When all links are connected, all routes are OK. Traffic from 134 to 125 goes through HQ-HAS-K1, from 134 to 179 goes through HQ-HAS-K1-K2 and from 125 to 179 goes through K1-K2, and vice-versa. All of these are main links. But when I drop link e.g. between HAS and K1, 125 and 179 subnets completely disappear from routing tables and completely disconnect from the entire network. In theory, when this link is dropped, traffic from 134 to 125 should go through K1Backup-K1 and traffic from 134 to 179 should go through K2Backup-K2.