Hi all,
I had tried shoot from every angle:
Can somebody kindly shed light , why the Summary Null route is currently missing from the ABR’s routing table ?
I understood the theory that said : [ when you use the Area Range command, a Summary route to null0 was supposed to be installed into the ABR’s routing table ].
I had labbed it up using Packet Tracer , with the following configurations, and this Summary Null route is currently missing from Router B’s table :
Please see my simple topology diagram :
Router B is the NSSA ABR , and is connecting to two areas : the backbone internal Router A, as well as connecting to Area 1 NSSA 's Router C (NSSA ASBR) .
**** Below is the configuration for NSSA ABR (Router B ):
hostname Router
no ip cef
no ipv6 cef
spanning-tree mode pvst
interface FastEthernet0/0
ip address 10.1.2.2 255.255.255.0
interface FastEthernet0/1
ip address 1.1.1.1 255.255.255.0
router ospf 24
log-adjacency-changes
area 0 range 10.0.0.0 255.0.0.0
area 1 nssa
network 10.0.0.0 0.255.255.255 area 0
network 1.0.0.0 0.255.255.255 area 1
!
ip classless
!
ip flow-export version 9
!
no cdp run
!
end
**** Below is the configuration for the Backbone internal Router A:
hostname Router
no ip cef
no ipv6 cef
spanning-tree mode pvst
!
interface FastEthernet0/0
ip address 10.1.1.1 255.255.255.0
!
interface FastEthernet0/1
ip address 10.1.2.1 255.255.255.0
!
router ospf 24
log-adjacency-changes
network 10.0.0.0 0.255.255.255 area 0
!
ip classless
ip flow-export version 9
end
**** Below is the configuration for NSSA ASBR (Router C ):
hostname Router
no ip cef
no ipv6 cef
spanning-tree mode pvst
!
interface FastEthernet0/0
ip address 1.1.1.2 255.255.255.0
!
interface FastEthernet0/1
ip address 172.16.1.1 255.255.255.0
!
router ospf 24
log-adjacency-changes
area 1 nssa
redistribute rip subnets
network 1.0.0.0 0.255.255.255 area 1
!
router rip
redistribute ospf 24
network 172.16.0.0
ip classless
ip flow-export version 9
end
!
**** Below is the configuration for the RIP Router D:
hostname Router
no ip cef
no ipv6 cef
spanning-tree mode pvst
!
interface FastEthernet0/0
ip address 172.16.1.2 255.255.255.0
!
interface FastEthernet0/1
ip address 172.16.2.1 255.255.255.0
!
router rip
network 172.16.0.0
!
ip classless
ip flow-export version 9
end
**** Here is the output “show ip route” for Router D: ***********
Gateway of last resort is not set
172.16.0.0/16 is variably subnetted, 2 subnets, 2 masks
C 172.16.1.0/24 is directly connected, FastEthernet0/0
L 172.16.1.2/32 is directly connected, FastEthernet0/0
***** Here is the output “show ip route” for Router C: ***********
Gateway of last resort is not set
1.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
C 1.1.1.0/24 is directly connected, FastEthernet0/0
L 1.1.1.2/32 is directly connected, FastEthernet0/0
O IA 10.0.0.0/8 [110/2] via 1.1.1.1, 02:13:08, FastEthernet0/0
172.16.0.0/16 is variably subnetted, 2 subnets, 2 masks
C 172.16.1.0/24 is directly connected, FastEthernet0/1
L 172.16.1.1/32 is directly connected, FastEthernet0/1
****** Here is the output “show ip route” for Router B: ***********
Gateway of last resort is not set
1.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
C 1.1.1.0/24 is directly connected, FastEthernet0/1
L 1.1.1.1/32 is directly connected, FastEthernet0/1
10.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
C 10.1.2.0/24 is directly connected, FastEthernet0/0
L 10.1.2.2/32 is directly connected, FastEthernet0/0
172.16.0.0/24 is subnetted, 1 subnets
O N2 172.16.1.0/24 [110/20] via 1.1.1.2, 01:56:15, FastEthernet0/1
**** Here is the output “show ip route” for Router A: ***********
Gateway of last resort is not set
1.0.0.0/24 is subnetted, 1 subnets
O IA 1.1.1.0/24 [110/2] via 10.1.2.2, 02:11:36, FastEthernet0/1
10.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
C 10.1.2.0/24 is directly connected, FastEthernet0/1
L 10.1.2.1/32 is directly connected, FastEthernet0/1
172.16.0.0/24 is subnetted, 1 subnets
O E2 172.16.1.0/24 [110/20] via 10.1.2.2, 02:11:36, FastEthernet0/1
Much Appreciated for your good trouble shooting knowledge 
!!!