Troubleshooting OSPF Route Advertisement

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 :smile: !!!