In this part of our blog series on OSPF area types, our Area 11 is
going to undergo a major flashback! The area is going to be reintroduced
to an early 1980′s American stereotype called Valley Girls and their
Valspeak. The area is no longer going to be Stubby, but it is going to
be like. . .like Totally Stubby! Lets review how we left Area 11 and how
things looked when it was just a Stub area:
Now lets make that Area 11 Totally Stubby and see what happens. All we need to do is go to the Area Border Router (ABR; R2), and add the no-summary keyword to the previous area 11 stub command. Notice this keyword only needs to be on the ABR. While you could add it to each and every area stub command in Area 11, it would have no effect and the proctor would question your abilities.
OK. Now that we have made the Totally Stubby configuration, lets examine the OSPF Database and IP Routing table on R3:
Please join us in the next part of this series where we examine the equally, cleverly-named, Not-So-Stubby Area.
R3#show ip ospf database
OSPF Router with ID (3.3.3.3) (Process ID 1)
Router Link States (Area 11)
Link ID ADV Router Age Seq# Checksum Link count
2.2.2.2 2.2.2.2 7 0x80000005 0x001A23 1
3.3.3.3 3.3.3.3 6 0x80000005 0x00D85C 1
Net Link States (Area 11)
Link ID ADV Router Age Seq# Checksum
192.168.1.3 3.3.3.3 6 0x80000004 0x004D5E
Summary Net Link States (Area 11)
Link ID ADV Router Age Seq# Checksum
0.0.0.0 2.2.2.2 33 0x80000001 0x0075C0
10.10.10.0 2.2.2.2 33 0x80000003 0x0062AA
172.16.10.0 2.2.2.2 33 0x80000003 0x00E181
R3#
R3#show ip route
Gateway of last resort is 192.168.1.2 to network 0.0.0.0
172.16.0.0/24 is subnetted, 1 subnets
O IA 172.16.10.0 [110/21] via 192.168.1.2, 00:01:23, FastEthernet0/0
10.0.0.0/24 is subnetted, 1 subnets
O IA 10.10.10.0 [110/20] via 192.168.1.2, 00:01:23, FastEthernet0/0
C 192.168.1.0/24 is directly connected, FastEthernet0/0
O*IA 0.0.0.0/0 [110/11] via 192.168.1.2, 00:01:23, FastEthernet0/0
R3#
The Stub area configuration wiped out any Type 4 and Type 5
LSAs in Area 11 and gave us the default route to the Area Border Router
(ABR) in order to reach those prefixes. Like way cool, man! OK, now I
sound like Scott Morris. Now lets make that Area 11 Totally Stubby and see what happens. All we need to do is go to the Area Border Router (ABR; R2), and add the no-summary keyword to the previous area 11 stub command. Notice this keyword only needs to be on the ABR. While you could add it to each and every area stub command in Area 11, it would have no effect and the proctor would question your abilities.
OK. Now that we have made the Totally Stubby configuration, lets examine the OSPF Database and IP Routing table on R3:
R3#show ip ospf database OSPF Router with ID (3.3.3.3) (Process ID 1) Router Link States (Area 11) Link ID ADV Router Age Seq# Checksum Link count 2.2.2.2 2.2.2.2 216 0x80000002 0x002020 1 3.3.3.3 3.3.3.3 215 0x80000002 0x00DE59 1 Net Link States (Area 11) Link ID ADV Router Age Seq# Checksum 192.168.1.3 3.3.3.3 215 0x80000001 0x00535B Summary Net Link States (Area 11) Link ID ADV Router Age Seq# Checksum 0.0.0.0 2.2.2.2 24 0x80000002 0x0073C1 R3#show ip route Gateway of last resort is 192.168.1.2 to network 0.0.0.0 C 192.168.1.0/24 is directly connected, FastEthernet0/0 O*IA 0.0.0.0/0 [110/11] via 192.168.1.2, 00:11:07, FastEthernet0/0 R3#Now I am reminded of a famous episode of the American television hit, Seinfeld. We have major shrinkage! Notice the Totally Stubby configuration has gone a step further than the Stub Area config. It not only wiped out the LSA Type 4s and 5s, but it also removed the LSA Type 3s. Those were the Summary LSAs about prefixes within our OSPF domain, but in other areas. In fact, the only LSA Type 3 we have left is the special, default route generated by the ABR. Boy is that route important now. It is the only hope of this router reaching any prefixes outside of the area.
Please join us in the next part of this series where we examine the equally, cleverly-named, Not-So-Stubby Area.
