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Chapter 5
Interconnecting OSPF Areas
Not-so-stubby area (NSSA) Like a stub area, a not-so-stubby area does
not receive Type 5 LSAs. However, sometimes there is a need, on a limited
basis, to import external routes. Such a situation is where NSSAs are use-
ful. The NSSA imports external routes (Type 7 LSAs), via route redistri-
bution, and then translates these Type 7 LSAs into Type 5 LSAs.
Basic Multi-area Configuration
C
onsider the multi-area OSPF network shown in Figure 5.3. To
review some of the router classifications that we previously discussed, notice
that RouterA would be classified as both an internal router and a backbone
router. Also, RouterB would be classified as both a backbone router and an
area border router. Finally, RouterC would be classified as an internal
router.
F I G U R E 5 . 3
Sample multi-area configuration
RouterA
interface Ethernet0
ip address 1.1.1.1 255.255.255.0
!
interface Ethernet1
ip address 1.1.2.1 255.255.255.0
!
router ospf 70
network 1.1.1.0 0.0.0.255 area 0
network 1.1.2.0 0.0.0.255 area 0
Area 1
Area 0
1.1.4.1/24
1.1.1.1/24
1.1.3.2/24
1.1.2.1/24
1.1.3.1/24
1.1.2.2/24
e0
e1
e0
e1
e0
e1
Ethernet
Ethernet
RouterC
RouterB
RouterA
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