個人理解,時間關係,寫的比較亂,還請包涵。
拓撲:
R2爲ASBR,在R1上看到R2發過來的LSA5類的FA不爲零,爲一個單播地址
關鍵配置:
[R1]dis cur
#
sysname R1
#
router id 91.1.1.1
#
interface GigabitEthernet0/0/0
ip address123.1.1.1 255.255.255.0
#
interface LoopBack0
ip address1.1.1.1 255.255.255.0
#
ospf 10
area 0.0.0.0
network1.1.1.1 0.0.0.0
network123.1.1.1 0.0.0.0
#
ip route-static 0.0.0.0 0.0.0.0GigabitEthernet0/0/0
#
dis cur
#
sysname R2
#
router id 92.2.2.2
#
interface GigabitEthernet0/0/0
ip address 123.1.1.2 255.255.255.0
undo icmp redirect send
#
interface LoopBack0
ip address 2.2.2.2 255.255.255.0
#
ospf 10
import-route static
area 0.0.0.0
network 2.2.2.2 0.0.0.0
network 123.1.1.2 0.0.0.0
#
ip route-static 3.3.3.3255.255.255.255 123.1.1.3
#
[R3]dis cur
#
sysname R3
#
router id 93.3.3.3
#
interface GigabitEthernet0/0/0
ip address 123.1.1.3 255.255.255.0
#
interface LoopBack0
ip address 3.3.3.3 255.255.255.0
#
ip route-static 0.0.0.0 0.0.0.0GigabitEthernet0/0/0
#
主要的配置寫在R2上,其中
interface GigabitEthernet0/0/0
ip address 123.1.1.2 255.255.255.0
undo icmp redirect send
關掉ICMP重定向只是說明IP重定向和OSPF的FA之間沒有太大聯繫
其它就是注意一點,FA地址非零條件之一就是要爲它產生一個單播地址:
ip route-static 3.3.3.3255.255.255.255 123.1.1.3
這個123.1.1.3就是爲FA產生的單播地址,會把它寫入LSA5類的FA中,以此指導R1的最優路由
下面是對比R2把123.1.1.3地址寫入FA前後:
[R1]dis ospf lsdb ase
OSPF Process 10 with Router ID 91.1.1.1
Link State Database
Type : External
Ls id : 3.3.3.3
Advrtr : 92.2.2.2
Ls age : 86
Len : 36
Options : E
seq# : 80000001
chksum : 0xb57
Netmask : 255.255.255.255
TOS 0 Metric: 1
E type : 2
Forwarding Address : 0.0.0.0
Tag : 1
Priority : Medium
[R1]dis ospf lsdb ase
OSPFProcess 10 with Router ID 91.1.1.1
Link State Database
Type : External
Ls id : 3.3.3.3
Advrtr : 92.2.2.2
Ls age : 11
Len : 36
Options : E
seq# : 80000001
chksum : 0x9c45
Netmask : 255.255.255.255
TOS 0 Metric: 1
E type : 2
Forwarding Address : 123.1.1.3
Tag : 1
Priority : Medium
當R1收到ASBR的R2發來的LSA5類地址有FA不爲零時,R1去訪問該地址時,首先封裝ARP,去以太網上找這到FA對應的MAC地址,當收到對方回覆後,IP包的封裝就成功了後面的通信就OK了,如下wireshark抓包演示,在R2上ping3.3.3.3的通信抓包: