R1：

interface Tunnel12

ip address 192.168.12.1 255.255.255.0

ip ospf 1 area 0

tunnel source 123.123.123.1

tunnel destination 123.123.123.2

!

interface Tunnel13

ip address 192.168.13.1 255.255.255.0

ip ospf 1 area 0

tunnel source 123.123.123.1

tunnel destination 123.123.123.3

!

interface Ethernet0/0

ip address 123.123.123.1 255.255.255.0

half-duplex

no shutdown

!

interface Ethernet0/1

ip address 14.14.14.1 255.255.255.0

half-duplex

no shutdown

!

router ospf 1

router-id 1.1.1.1

log-adjacency-changes

network 14.14.14.1 0.0.0.0 area 0

!

R2：

interface Tunnel12

ip address 192.168.12.2 255.255.255.0

ip ospf 1 area 0

tunnel source 123.123.123.2

tunnel destination 123.123.123.1

!

interface Tunnel23

ip address 192.168.23.2 255.255.255.0

ip ospf 1 area 0

tunnel source 123.123.123.2

tunnel destination 123.123.123.3

!

interface Ethernet0/0

ip address 123.123.123.2 255.255.255.0

half-duplex

no shutdown

!

interface Ethernet0/1

ip address 25.25.25.2 255.255.255.0

half-duplex

no shutdown

!

router ospf 1

router-id 2.2.2.2

log-adjacency-changes

network 25.25.25.2 0.0.0.0 area 0

!

R3：

interface Tunnel13

ip address 192.168.13.3 255.255.255.0

ip ospf 1 area 0

tunnel source 123.123.123.3

tunnel destination 123.123.123.1

!

interface Tunnel23

ip address 192.168.23.3 255.255.255.0

ip ospf 1 area 0

tunnel source 123.123.123.3

tunnel destination 123.123.123.2

!

interface Ethernet0/0

ip address 123.123.123.3 255.255.255.0

half-duplex

no shutdown

!

interface Ethernet0/1

ip address 36.36.36.3 255.255.255.0

half-duplex

no shutdown

!

router ospf 1

router-id 3.3.3.3

log-adjacency-changes

network 36.36.36.3 0.0.0.0 area 0

!

R4:

interface Loopback0

ip address 4.4.4.4 255.255.255.0

!

interface Ethernet0/1

ip address 14.14.14.4 255.255.255.0

half-duplex

no shutdown

router ospf 1

router-id 4.4.4.4

log-adjacency-changes

network 4.4.4.4 0.0.0.0 area 0

network 14.14.14.4 0.0.0.0 area 0

!

R5:

interface Loopback0

ip address 5.5.5.5 255.255.255.0

!

interface Ethernet0/1

ip address 25.25.25.5 255.255.255.0

half-duplex

no shutdown

router ospf 1

router-id 5.5.5.5

log-adjacency-changes

network 5.5.5.5 0.0.0.0 area 0

network 25.25.25.5 0.0.0.0 area 0

!

R6:

interface Loopback0

ip address 6.6.6.6 255.255.255.0

!

interface Ethernet0/1

ip address 36.36.36.6 255.255.255.0

half-duplex

no shutdown

router ospf 1

router-id 6.6.6.6

log-adjacency-changes

network 6.6.6.6 0.0.0.0 area 0

network 36.36.36.6 0.0.0.0 area 0

!