Information Technology Reference
In-Depth Information
The following commands are added to all routers in area 10 to make the area a stub area.
router ospf 100
area 10 stub
The link-state database and routing table on Router 7 had six summary network addresses and
one external address before area 10 became a stub network. It still has the six summary network
addresses plus an additional one for the injected default route. The databases no longer list the
external route. This is not much of an improvement. Example 8-17 displays the new link-state
database and routing table on Router 7 in Figure 8-7. Nonrelevant entries have been removed
from the link-state database.
Example 8-17 Link-State Database and Routing Table for Stub Area
Router7#show ip ospf database
OSPF Router with ID (192.16.100.5) (Process ID 100)
...
Summary Net Link States (Area 10)
Link ID ADV Router Age Seq# Checksum
192.16.100.2 192.16.100.4 1122 0x80000001 0xEAD6
192.16.100.3 192.16.100.4 1122 0x80000001 0x631D
192.16.100.4 192.16.100.4 56 0x80000004 0x6C5A
192.16.100.16 192.16.100.4 1137 0x8000000B 0xE5D3
192.16.100.32 192.16.100.4 840 0x80000001 0x4029
192.16.100.240 192.16.100.4 322 0x80000003 0xF79C
0.0.0.0 192.16.100.4 460 0x80000001 0x9371
...
Router7#show ip route
Gateway of last resort is 192.16.100.245 to network 0.0.0.0
192.16.100.0/24 is variably subnetted, 9 subnets, 4 masks
C 192.16.100.128/27 is directly connected, Ethernet0
C 192.16.100.244/30 is directly connected, Serial0.1
O IA 192.16.100.240/30 [110/138] via 192.16.100.245, 00:05:32, Serial0.1
O IA 192.16.100.32/28 [110/148] via 192.16.100.245, 00:05:32, Serial0.1
O IA 192.16.100.16/28 [110/74] via 192.16.100.245, 00:05:32, Serial0.1
O IA 192.16.100.4/32 [110/65] via 192.16.100.245, 00:05:33, Serial0.1
C 192.16.100.5/32 is directly connected, Loopback0
O IA 192.16.100.2/32 [110/75] via 192.16.100.245, 00:05:33, Serial0.1
O IA 192.16.100.3/32 [110/139] via 192.16.100.245, 00:05:33, Serial0.1
O*IA 0.0.0.0/0 [110/65] via 192.16.100.245, 00:00:09, Serial0.1
The no-summary keyword makes the area totally stubby versus a regular stub area. It is added
to the area 10 ABR routers as follows:
router ospf 100
area 10 stub no-summary
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