OSPF虛鏈路解決非直連區(qū)域以及解決Area0被分割
首先靜態(tài)IP，并且宣告到OSPF進程中，注意宣告到不同區(qū)域；
[AR1]
router id 10.0.1.1
interface GigabitEthernet0/0/0
ip address 10.0.12.1 255.255.255.0
interface GigabitEthernet0/0/1
ip address 10.0.13.1 255.255.255.0
interface LoopBack0
ip address 10.0.1.1 255.255.255.255
ospf 1
area 0.0.0.0
network 10.0.1.1 0.0.0.0
network 10.0.12.1 0.0.0.0
area 0.0.0.1
network 10.0.13.1 0.0.0.0
[AR2]
router id 10.0.2.2
interface GigabitEthernet0/0/0
ip address 10.0.12.2 255.255.255.0
interface GigabitEthernet0/0/1
ip address 10.0.23.2 255.255.255.0
interface LoopBack0
ip address 10.0.2.2 255.255.255.255
ospf 1
area 0.0.0.0
network 10.0.2.2 0.0.0.0
network 10.0.12.2 0.0.0.0
area 0.0.0.1
network 10.0.23.2 0.0.0.0
[AR3]
router id 10.0.3.3
interface GigabitEthernet0/0/0
ip address 10.0.34.3 255.255.255.0
interface GigabitEthernet2/0/0
ip address 10.0.13.3 255.255.255.0
interface GigabitEthernet2/0/1
ip address 10.0.23.3 255.255.255.0
interface LoopBack0
ip address 10.0.3.3 255.255.255.255
ospf 1
area 0.0.0.1
network 10.0.3.3 0.0.0.0
network 10.0.13.3 0.0.0.0
network 10.0.23.3 0.0.0.0
area 0.0.0.2
network 10.0.34.3 0.0.0.0
[AR4]
router id 10.0.4.4
interface GigabitEthernet0/0/0
ip address 10.0.34.4 255.255.255.0
interface LoopBack0
ip address 10.0.4.4 255.255.255.255
ospf 1
area 0.0.0.2
network 10.0.4.4 0.0.0.0
network 10.0.34.4 0.0.0.0
查看AR3上午OSPF鄰居關(guān)系，可以看到AR3的鄰居關(guān)系都是Full狀態(tài)；
<AR3>display ospf peer bri
OSPF Process 1 with Router ID 10.0.3.3
Peer Statistic Information
----------------------------------------------------------------------------
Area
Id Interface Neighbor id State
0.0.0.1 GigabitEthernet2/0/0 10.0.1.1 Full
0.0.0.1 GigabitEthernet2/0/1 10.0.2.2 Full
0.0.0.2 GigabitEthernet0/0/0 10.0.4.4 Full
----------------------------------------------------------------------------
查看AR4的LSDB，發(fā)現(xiàn)沒有關(guān)于Area0中的10.0.1.1/32和10.0.2.2/32的LSA，也沒有任何其他Area的LSA，僅僅只有本區(qū)域的Type1 LSA和Type2 LSA，因為Area2并未與Area0直連；
所以需要使用虛鏈路使得Area2與Area0在邏輯上互相連接起來；
在AR3和AR1上進行配置；
[AR3]ospf 1
[AR3-ospf-1]area 1
[AR3-ospf-1-area-0.0.0.1]vlink-peer 10.0.1.1
[AR1]ospf 1
[AR1-ospf-1]area 1
[AR1-ospf-1-area-0.0.0.1]vlink-peer 10.0.3.3
之后再AR1上查看虛鏈路的狀態(tài)，發(fā)現(xiàn)已經(jīng)建立了虛連接，并且Full狀態(tài)；
[AR1]display ospf vlink
OSPF Process 1 with Router ID 10.0.1.1
Virtual Links
Virtual-link Neighbor-id -> 10.0.3.3, Neighbor-State: Full
Interface: 10.0.13.1 (GigabitEthernet0/0/1)
Cost: 1
State: P-2-P Type: Virtual
Transit
Area: 0.0.0.1
Timers: Hello 10 , Dead 40 , Retransmit 5 ,
Transmit Delay 1
GR
State: Normal
之后在AR4上查看LSDB，出現(xiàn)了AR3通告的Type3類LSA；
<AR4>display ospf lsdb
OSPF Process 1 with Router ID 10.0.4.4
Link State Database
Area: 0.0.0.2
Type
LinkState ID AdvRouter Age
Len Sequence Metric
Router
10.0.3.3 10.0.3.3 174
36 80000006 1
Router
10.0.4.4 10.0.4.4 1521
48 80000005 0
Network
10.0.34.3 10.0.3.3 1517
32 80000002 0
Sum-Net
10.0.13.0 10.0.3.3 174
28 80000001 1
Sum-Net
10.0.12.0 10.0.3.3 174
28 80000001 2
Sum-Net
10.0.3.3 10.0.3.3 174
28 80000001 0
Sum-Net
10.0.2.2 10.0.3.3 174
28 80000001 1
Sum-Net
10.0.1.1 10.0.3.3 174
28 80000001 1
Sum-Net
10.0.23.0 10.0.3.3 174
28 80000001 1
同樣也可以在AR3和AR2之間建立虛鏈路；
[AR3-ospf-1-area-0.0.0.1]vlink-peer 10.0.2.2
[AR2-ospf-1-area-0.0.0.1]vlink-peer 10.0.3.3
之后在AR3上查看虛鏈路的狀態(tài)，可以看到兩條等價的虛鏈路，cost均為1；
[AR3-ospf-1]display ospf vlink
OSPF Process 1 with Router ID 10.0.3.3
Virtual Links
Virtual-link Neighbor-id -> 10.0.1.1, Neighbor-State: Full
Interface: 10.0.13.3 (GigabitEthernet2/0/0)
Cost: 1
State: P-2-P Type: Virtual
Transit Area: 0.0.0.1
Timers: Hello 10 , Dead 40 , Retransmit 5 ,
Transmit Delay 1
GR
State: Normal
Virtual Links
Virtual-link Neighbor-id -> 10.0.2.2, Neighbor-State: Full
Interface: 10.0.23.3 (GigabitEthernet2/0/1)
Cost: 1
State: P-2-P Type: Virtual
Transit Area: 0.0.0.1
Timers: Hello 10 , Dead 40 , Retransmit 5 ,
Transmit Delay 1
GR
State: Normal
可以修改虛鏈路的接口開銷值，形成一條備用鏈路；
在AR3的G2/0/1和AR2的G0/0/1上，修改cost值為10；
[AR3]int g 2/0/1
[AR3-GigabitEthernet2/0/1]ospf cost 10
[AR2]int g 0/0/1
[AR2-GigabitEthernet0/0/1]ospf cost 10
之后可以看到，AR3到AR2的虛鏈路的cost值變?yōu)榱?0；
[AR3]display ospf vlink
OSPF Process 1 with Router ID 10.0.3.3
Virtual Links
Virtual-link Neighbor-id -> 10.0.1.1, Neighbor-State: Full
Interface: 10.0.13.3 (GigabitEthernet2/0/0)
Cost: 1
State: P-2-P Type: Virtual
Transit Area: 0.0.0.1
Timers: Hello 10 , Dead 40 , Retransmit 5 ,
Transmit Delay 1
GR
State: Normal
Virtual Links
Virtual-link Neighbor-id -> 10.0.2.2, Neighbor-State: Full
Interface: 10.0.23.3 (GigabitEthernet2/0/1)
Cost: 10
State: P-2-P Type: Virtual
Transit Area: 0.0.0.1
Timers: Hello 10 , Dead 40 , Retransmit 5 ,
Transmit Delay 1
GR
State: Normal
虛鏈路還能作為Area0中的鏈路的冗余備份；
AR1和AR2之間只有單條鏈路，一旦出現(xiàn)故障，就會導(dǎo)致Area0被分割，所以可以以Area1位傳輸區(qū)域，在AR1和AR2之間建立一條虛鏈路作為冗余備份；
[AR1]ospf 1
[AR1-ospf-1]area 1
[AR1-ospf-1-area-0.0.0.1]vlink-peer 10.0.2.2
[AR2]ospf 1
[AR2-ospf-1]area 1
[AR2-ospf-1-area-0.0.0.1]vlink-peer 10.0.1.1
之后在AR1上查看虛鏈路的信息，可以看到AR1和AR2之間的虛鏈路的cost是11；
[AR1]display ospf vlink
OSPF Process 1 with Router ID 10.0.1.1
Virtual Links
Virtual-link Neighbor-id -> 10.0.2.2, Neighbor-State: Full
Interface: 10.0.13.1 (GigabitEthernet0/0/1)
Cost: 11
State: P-2-P Type: Virtual
Transit Area: 0.0.0.1
Timers:
Hello 10 , Dead 40 , Retransmit 5 , Transmit Delay 1
GR
State: Normal
Virtual Links
Virtual-link Neighbor-id -> 10.0.3.3, Neighbor-State: Full
Interface: 10.0.13.1 (GigabitEthernet0/0/1)
Cost: 1
State: P-2-P Type: Virtual
Transit Area: 0.0.0.1
Timers: Hello 10 , Dead 40 , Retransmit 5 ,
Transmit Delay 1
GR
State: Normal
在AR1上使用tracert測試，目前AR1和AR2之間是使用直連鏈路進行通訊的；
[AR1]tracert 10.0.2.2
traceroute to
10.0.2.2(10.0.2.2), max hops: 30 ,packet length: 40,press CTRL_C to
break
1
10.0.12.2 40 ms 30 ms 10 ms
關(guān)閉AR1的G0/0/0，模擬鏈路故障；
[AR1]int g 0/0/0
[AR1-GigabitEthernet0/0/0]shutdown
再次tracert，可以看到使用了虛鏈路進行通訊，經(jīng)過了AR3；
[AR1]tracert 10.0.2.2
traceroute to
10.0.2.2(10.0.2.2), max hops: 30 ,packet length: 40,press CTRL_C to
break
1
10.0.13.3 30 ms 20 ms 30 ms
2
10.0.23.2 30 ms 20 ms 20 ms
?
王亦軍 老師 上海騰科
2018.03.23 提交上傳?
