We will be using the same topology from my previous blogtorials. So let's get started.
Objective: To configure Area 1 as a Totally Stubby Area and see how it affects the routing table of R5 (in Area 1).
Below is the routing table for R5 before we make Area 1 into a totally stubby area. Notice E2/IA routes.
R5#sh ip route
<-- output shortened -->
172.16.0.0/16 is variably subnetted, 5 subnets, 2 masks
C 172.16.5.0/24 is directly connected, Loopback0
O IA 172.16.4.1/32 [110/2] via 10.1.1.4, 00:00:03, FastEthernet1/0
O E2 172.16.6.0/24 [110/20] via 10.1.1.4, 00:00:03, FastEthernet1/0
O E2 172.16.2.0/24 [110/20] via 10.1.1.4, 00:00:03, FastEthernet1/0
O E2 172.16.3.0/24 [110/20] via 10.1.1.4, 00:00:03, FastEthernet1/0
10.0.0.0/24 is subnetted, 3 subnets
O E2 10.2.2.0 [110/20] via 10.1.1.4, 00:00:03, FastEthernet1/0
C 10.1.1.0 is directly connected, FastEthernet1/0
O IA 10.0.0.0 [110/2] via 10.1.1.4, 00:00:03, FastEthernet1/0
Now let's configure both R4 and R5 so area 1 becomes a totally stubby area.
R4#sh run | sec ospf
router ospf 1
log-adjacency-changes
area 1 stub no-summary ** This command states that area 1 is a totally stubby area. Remember Area type is one of the criteria which has to match in-order to form OSPF neighbor relationship **
network 10.0.0.0 0.0.0.255 area 0
network 10.1.1.0 0.0.0.255 area 1
network 172.16.4.0 0.0.0.255 area 0
network 192.168.1.0 0.0.0.255 area 0
R5#sh run | sec ospf
router ospf 1
log-adjacency-changes
area 1 stub no-summary ** This command states that area 1 is a totally stubby area. Remember Area type is one of the criteria which has to match in-order to form OSPF neighbor relationship **
network 10.1.1.0 0.0.0.255 area 1
network 10.3.3.0 0.0.0.255 area 2
network 172.16.5.0 0.0.0.255 area 1
network 192.168.1.0 0.0.0.255 area 0
Now let's look at 'sh ip route' on R5 in Area 1 which is now a 'totally stubby area'.
R5#sh ip route
<-- output shortened -->
172.16.0.0/24 is subnetted, 1 subnets
C 172.16.5.0 is directly connected, Loopback0
10.0.0.0/24 is subnetted, 1 subnets
C 10.1.1.0 is directly connected, FastEthernet1/0
O*IA 0.0.0.0/0 [110/2] via 10.1.1.4, 00:01:33, FastEthernet1/0 ** Nothing but a default summary route **
So that's how easy it is to reduce the size of the OSPF database 'area x stub no-summary'.
Wonder if some surfer in California came up with this "Dude that is a totally stubby area" :)
Many more articles to come so stay tuned!! If you like my posts please subscribe!!
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