OSPF & Virtual Link

sys
sysn R1
int g0/0/0
ip add 172.0.10.1 24
ospf 1 router-id 255.255.255.255
area 0
net 172.0.10.0 0.0.0.255

sys
sysn R2
int g0/0/0
ip add 172.0.10.2 24
int g0/0/1
ip add 172.0.20.1 24
ospf 1 router-id 2.2.2.2 
area 0
network 172.0.10.0 0.0.0.255 
area 1 
network 172.0.20.0 0.0.0.255 
vlink-peer 3.3.3.3

sys
sysn R3
int g0/0/0
ip add 172.0.20.2 24
int g0/0/1
ip add 172.0.30.1 24
ospf 1 router-id 3.3.3.3 
area 1 
network 172.0.20.0 0.0.0.255 
vlink-peer 2.2.2.2
vlink-peer 255.255.255.255
area 2 
network 172.0.30.0 0.0.0.255 
vlink-peer 4.4.4.4

sys
sysn R4
int g0/0/0
ip add 172.0.30.2 24
int g0/0/1
ip add 172.0.40.1 24
ospf 1 router-id 4.4.4.4 
area 2 
network 172.0.30.0 0.0.0.255 
vlink-peer 3.3.3.3
area 3 
network 172.0.40.0 0.0.0.255 
vlink-peer 5.5.5.5

sys
sysn R5
int g0/0/0
ip add 172.0.40.2 24
ospf 1 router-id 5.5.5.5 
area 3 
network 172.0.40.0 0.0.0.255 
vlink-peer 4.4.4.4