OSPF NSSA区域中的默认路由

zdc253212956

　　Router 1.1.1.1


Current configuration:
hostname r1.1.1.1
interface Loopback0
ip address 1.1.1.1 255.0.0.0
interface Serial2/1/0
ip address 5.0.0.1 255.0.0.0
router ospf 2
network 5.0.0.0 0.255.255.255 area 1
area 1 nssa
end
　　


　　Router 2.2.2.2


Current configuration:
hostname r2.2.2.2
interface Loopback0
ip address 2.2.2.2 255.0.0.0
interface Serial0/1/0
ip address 5.0.0.2 255.0.0.0
interface ATM1/0.20
ip address 6.0.0.2 255.0.0.0
router ospf 2
network 5.0.0.0 0.255.255.255 area 1
network 6.0.0.0 0.255.255.255 area 0
area 1 nssa default-information originate
end

Examine the OSPF Database in a Not So Stubby Area

　　To see how the OSPF Database looks, use the show ip ospf database command.

r2.2.2.2#show ip ospf database
OSPF Router with ID (2.2.2.2) (Process ID 2)
Router Link States (Area 0)
Link ID    ADV Router     Age     Seq#          Checksum   Link count
2.2.2.2    2.2.2.2        600     0x80000001    0x9583          1
Summary Net Link States (Area 0)
Link ID    ADV Router      Age     Seq#          Checksum
5.0.0.0     2.2.2.2        600     0x80000001    0x8E61
Router Link States (Area 1)
Link ID    ADV Router     Age     Seq#           Checksum   Link count
1.1.1.1    1.1.1.1        864     0x8000005E     0xD350         2
2.2.2.2    2.2.2.2        584     0x8000001E     0xF667         2
Summary Net Link States (Area 1)
Link ID    ADV Router     Age     Seq#          Checksum
6.0.0.0    2.2.2.2        585     0x80000004    0xA87C
Type-7 AS External Link States (Area 1)
Link ID    ADV Router     Age     Seq#          Checksum   Tag
0.0.0.0    2.2.2.2        601     0x80000001    0xD0D8      0

　　The ABR for the NSSA originates a type 7 and an LSA with a link ID of 0.0.0.0. This is a result of the area 1 nssa default-information-originate command in its OSPF configuration.

r2.2.2.2#show ip ospf database nssa-external 0.0.0.0
OSPF Router with ID (2.2.2.2) (Process ID 2)
Type-7 AS External Link States (Area 1)
LS age: 650
Options: (No TOS-capability, No Type 7/5 translation, DC)
LS Type: AS External Link
Link State ID: 0.0.0.0 (External Network Number )
Advertising Router: 2.2.2.2
LS Seq Number: 80000001
Checksum: 0xD0D8
Length: 36
Network Mask: /0
Metric Type: 2 (Larger than any link state path)
TOS: 0
Metric: 1
Forward Address: 0.0.0.0
External Route Tag: 0

　　The ABR originates the 0.0.0.0 type 7 LSA, even though it does not have a default route.

r2.2.2.2#show ip route 0.0.0.0
% Network not in table
r1.1.1.1#show ip route ospf
O IA 6.0.0.0/8 [110/65] via 5.0.0.2, 00:00:18, Serial2/1/0
O*N2 0.0.0.0/0 [110/1] via 5.0.0.2, 00:00:18, Serial2/1/0