check that Area 234 is configured as Stub.
On Router 1
R1#sh ip ospf
Routing Process "ospf 1" with ID 1.1.1.1
Start time: 00:05:48.280, Time elapsed: 00:07:36.756
Supports only single TOS(TOS0) routes
Supports opaque LSA
Supports Link-local Signaling (LLS)
Supports area transit capability
Router is not originating router-LSAs with maximum metric
Initial SPF schedule delay 5000 msecs
Minimum hold time between two consecutive SPFs 10000 msecs
Maximum wait time between two consecutive SPFs 10000 msecs
Incremental-SPF disabled
Minimum LSA interval 5 secs
Minimum LSA arrival 1000 msecs
LSA group pacing timer 240 secs
Interface flood pacing timer 33 msecs
Retransmission pacing timer 66 msecs
Number of external LSA 0. Checksum Sum 0x000000
Number of opaque AS LSA 0. Checksum Sum 0x000000
Number of DCbitless external and opaque AS LSA 0
Number of DoNotAge external and opaque AS LSA 0
Number of areas in this router is 1. 0 normal 1 stub 0 nssa
Number of areas transit capable is 0
External flood list length 0
Area 234
Number of interfaces in this area is 3
It is a stub area
Area has no authentication
SPF algorithm last executed 00:04:48.012 ago
SPF algorithm executed 4 times
Area ranges are
Number of LSA 23. Checksum Sum 0x154B32
Number of opaque link LSA 0. Checksum Sum 0x000000
Number of DCbitless LSA 0
Number of indication LSA 0
Number of DoNotAge LSA 0
Flood list length 0
R1#sh ip ospf database database-summary
OSPF Router with ID (1.1.1.1) (Process ID 1)
Area 234 database summary
LSA Type Count Delete Maxage
you can there is no LSA 5 in database summary.
R1#sh ip ospf database summary 0.0.0.0
This command lists all summary (LSA 3) with prefix 0.0.0.0. It list two such LSAs from 3.3.3.3 and 4.4.4.4
OSPF Router with ID (1.1.1.1) (Process ID 1)
Summary Net Link States (Area 234)
Routing Bit Set on this LSA
LS age: 1156
Options: (No TOS-capability, DC, Upward)
LS Type: Summary Links(Network)
Link State ID: 0.0.0.0 (summary Network Number)
Advertising Router: 3.3.3.3
LS Seq Number: 80000001
Checksum: 0x57DA
Length: 28
Network Mask: /0
TOS: 0 Metric: 1
Routing Bit Set on this LSA
LS age: 1155
Options: (No TOS-capability, DC, Upward)
LS Type: Summary Links(Network)
Link State ID: 0.0.0.0 (summary Network Number)
Advertising Router: 4.4.4.4
LS Seq Number: 80000001
Checksum: 0x39F4
Length: 28
Network Mask: /0
TOS: 0 Metric: 1
Check the cost of default route generated by ABRs in Area 234
Router1
O*IA 0.0.0.0/0 [110/2] via 14.14.14.2, 00:15:23, FastEthernet0/0
[110/2] via 13.13.13.2, 00:15:23, FastEthernet2/0
both the ABRs are generated Default route with metric 1 in area 234
what if i want the packets to take route through router3 for networks in BackBone Area.
change the area default cost at ABRs.
R3(config)#router ospf 1
area 234 defalut-cost 10
R4(config)#router ospf 1
area 234 defalut-cost 20
Any internal router will select low cost path for exit.
R1#sh ip route | in 0.0.0.0
Gateway of last resort is 13.13.13.2 to network 0.0.0.0
O*IA 0.0.0.0/0 [110/11] via 13.13.13.2, 00:00:15, FastEthernet2/0
Default route on Router4 is available when router3 will fail.
Change the state of R1 interface F2/0 and F1/0
int f2/0
sh
int f1/0
sh
Now the Router1 have no route to R3, and it will chose R4
R1#sh ip route | in 0.0.0.0
Gateway of last resort is 14.14.14.2 to network 0.0.0.0
O*IA 0.0.0.0/0 [110/21] via 14.14.14.2, 00:00:08, FastEthernet0/0
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