Here some examples of advertising your loopback interfaces into OSPF

1. OSPF loopback advertisement:
Advertise the loopback0 network into area 17.
These networks should appear in all other OSPF enabled routers with a /24 subnet mask.

interface loopback 0
ip ospf network point-to-point
!
router ospf 1
network 150.1.1.1 0.0.0.0 area 17

2. OSPF loopback advertisement:
Advertise the loopback 0 network of R4 into OSPF.
This network should appear in all other OSPF enable routers with a /24 subnet mask.
This network should not be associated with any particular OSPF area.

router ospf 1
redistribute connected subnets route-map CONNECTED->OSPF
!
route-map CONNECTED->OSPF
match interface loopback0

3. OSPF loopback advertisement:
Advertise the loopback0 network of R3 into OSPF.
This network should appear in all other OSPF enabled routers with a /24 subnet mask.
This network should be associated with an OSPF area.
Do not use the ‘ip ospf network-type point-to-point’ command for this task.

router ospf 1
network 150.1.3.3 0.0.0.0 area 3
area 3 range 150.1.3.0 255.255.255.0

4. OSPF loopback advertisement:
Advertise the loopback0 network of R5 into OSPF.
This network should appear in all other OSPF enabled routers with a /24 subnet mask.
This network should not be associated with any particular OSPF area.
Do not use the ‘redistribute connected’ command for this task.
router rip
network 150.1.0.0
!
router ospf 1
redistribute rip subnets route-map RIP->OSPF
!
route-map RIP->OSPF permit 10
match interface loopback0