实验OSPF虚链路扩充骨干区域

Ospf非骨干区域必须与骨干区域相连，所以我们采用虚链路，使area1 ,area2为骨干区域area 0，非骨干区域area 2 与之逻辑上相连，以达到扩充骨干区域的目的
以下为物理TOPO图





以下为实际效果图:



配置如下:

r2#
interface Loopback0

ip address 2.2.2.2 255.255.255.0

ip ospf network point-to-point
!
interface Serial2/0

ip address 12.1.1.2 255.255.255.0
!
router ospf 10

router-id 2.2.2.2

network 2.2.2.0 0.0.0.255 area 0

network 12.1.1.0 0.0.0.255 area 0


r1#
interface Loopback0

ip address 1.1.1.1 255.255.255.0

ip ospf network point-to-point
!
interface Serial1/0

ip address 12.1.1.1 255.255.255.0
!
interface Serial2/0

ip address 13.1.1.1 255.255.255.0
!
router ospf 10

router-id 1.1.1.1

area 1 virtual-link 3.3.3.3

network 1.1.1.0 0.0.0.255 area 0

network 12.1.1.0 0.0.0.255 area 0

network 13.1.1.0 0.0.0.255 area 1
!
r3#
interface Loopback0

ip address 3.3.3.3 255.255.255.0

ip ospf network point-to-point
!
interface Serial1/0

ip address 13.1.1.3 255.255.255.0
!
interface Serial2/0

ip address 35.1.1.3 255.255.255.0
!
router ospf 10

router-id 3.3.3.3

area 1 virtual-link 1.1.1.1

area 3 virtual-link 5.5.5.5

network 3.3.3.0 0.0.0.255 area 1

network 13.1.1.0 0.0.0.255 area 1

network 35.1.1.0 0.0.0.255 area 3
!
r5#
interface Loopback0

ip address 5.5.5.5 255.255.255.0

ip ospf network point-to-point
!
interface Serial1/0

ip address 35.1.1.5 255.255.255.0
!
interface Serial2/0

ip address 45.1.1.5 255.255.255.0
!
router ospf 10

router-id 5.5.5.5

area 3 virtual-link 3.3.3.3

network 5.5.5.0 0.0.0.255 area 2

network 35.1.1.0 0.0.0.255 area 3

network 45.1.1.0 0.0.0.255 area 2
!

r4#
interface Loopback0

ip address 4.4.4.4 255.255.255.0

ip ospf network point-to-point
!
interface Serial1/0

ip address 45.1.1.4 255.255.255.0
!
router ospf 10

router-id 4.4.4.4

network 4.4.4.0 0.0.0.255 area 2

network 45.1.1.0 0.0.0.255 area 2
!
正常情况下，无虚链路时，R4的路由表为：
r4#sh ip route
Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP

D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area

N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2

E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP

i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS inter area

* - candidate default, U - per-user static route, o - ODR

P - periodic downloaded static route

Gateway of last resort is not set


4.0.0.0/24 is subnetted, 1 subnets
C
4.4.4.0 is directly connected, Loopback0

5.0.0.0/24 is subnetted, 1 subnets
O
5.5.5.0 [110/65] via 45.1.1.5, 00:01:44, Serial1/0

45.0.0.0/24 is subnetted, 1 subnets
C
45.1.1.0 is directly connected, Serial1/0

增加虚链路后，看R4路由表：
r4#
sh ip route
Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP

D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area

N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2

E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP

i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS inter area

* - candidate default, U - per-user static route, o - ODR

P - periodic downloaded static route

Gateway of last resort is not set


1.0.0.0/24 is subnetted, 1 subnets
O IA
1.1.1.0 [110/193] via 45.1.1.5, 00:06:24, Serial1/0

35.0.0.0/24 is subnetted, 1 subnets
O IA

35.1.1.0 [110/128] via 45.1.1.5, 00:06:24, Serial1/0

2.0.0.0/24 is subnetted, 1 subnets
O IA
2.2.2.0 [110/257] via 45.1.1.5, 00:06:24, Serial1/0

3.0.0.0/24 is subnetted, 1 subnets
O IA
3.3.3.0 [110/129] via 45.1.1.5, 00:06:24, Serial1/0

4.0.0.0/24 is subnetted, 1 subnets
C
4.4.4.0 is directly connected, Loopback0

5.0.0.0/24 is subnetted, 1 subnets
O
5.5.5.0 [110/65] via 45.1.1.5, 00:06:24, Serial1/0

12.0.0.0/24 is subnetted, 1 subnets
O IA
12.1.1.0 [110/256] via 45.1.1.5, 00:06:24, Serial1/0

13.0.0.0/24 is subnetted, 1 subnets
O IA
13.1.1.0 [110/192] via 45.1.1.5, 00:06:24, Serial1/0

45.0.0.0/24 is subnetted, 1 subnets
C
45.1.1.0 is directly connected, Serial1/0

可以看到：
R4有其他区域的路由，而它与骨干区域相隔2个区域，所以达到了扩充骨干区域的目的。

楼主都是实验呀,多点解析的,这样也许能懂一点,不过还是要谢谢的