一、拓撲圖:
二、配置說明與分析:
1、按照拓撲圖配置各路由器的IP位址和協定,并在R2和R5上做重分發,保證所有的鍊路的連通性。看一下R2上的重分發配置:
R2#show run
router ospf 1
log-adjacency-changes
redistribute rip metric 200 subnets (把RIP發進OSPF過來的cost 我定義為200)
network 172.16.255.0 0.0.0.3 area 0
!
router rip
redistribute ospf 1 metric 11 (把ospf 發進RIP過來的cost 我定義為 11)
network 192.168.1.0
2、那麼應該說通過R2這個路由後:
ospf 區域到rip區域後cost 将會為成為我們定義的值 11
Rip區域到ospf 區域後cost 将會成為我們定義的值 200
3、在RIP區域看一下ospf 區域過來的路由:
R1# sh ip route
Codes: C - connected, S - static, 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
i - IS-IS, su - IS-IS summary, 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
R 172.16.0.0/16 [120/11] via 192.168.1.2, 00:00:07, Serial1/1(ospf那邊過來的,RIP把它當R)
10.0.0.0/24 is subnetted, 1 subnets
C 10.1.1.0 is directly connected, Loopback0
C 192.168.1.0/24 is directly connected, Serial1/1
C 192.168.2.0/24 is directly connected, FastEthernet0/0
4、在OSPF區域看一下RIP區域過來的路由:
R3#show ip route
172.16.0.0/30 is subnetted, 3 subnets
C 172.16.255.0 is directly connected, Serial1/0
C 172.16.255.4 is directly connected, Serial1/1
O 172.16.255.8 [110/128] via 172.16.255.6, 00:49:26, Serial1/1
O E2 10.0.0.0/8 [110/200] via 172.16.255.1, 00:49:26, Serial1/0
O E2 192.168.1.0/24 [110/200] via 172.16.255.1, 00:49:26, Serial1/0 (通過R2過來的定義了200)
O E1 192.168.2.0/24 [110/328] via 172.16.255.6, 00:49:26, Serial1/1(通過R5過來的,那麼為什麼是328呢?這條路由經過R5過來的,它會以R5上的重分發的cost值計算,因為我在R5重釋出的時候做了redistribute rip metric 200 metric-type 1 subnets 這樣就會疊加經過ospf 區域的cost:RIPàOSPF (cost 200) + R4—>R5 (cost 64) + R3—>R4 (cost 64) = cost 328)
5、通過上面的圖示我們弄清了rip和ospf 區域的cost值之後,現在我們在R5上看一下路由表:
R5#show ip route
O 172.16.255.0 [110/192] via 172.16.255.9, 00:03:00, Serial1/0
O 172.16.255.4 [110/128] via 172.16.255.9, 00:03:00, Serial1/0
C 172.16.255.8 is directly connected, Serial1/0
O E2 10.0.0.0/8 [110/200] via 172.16.255.9, 00:02:59, Serial1/0 (居然繞了4個路由器)
O E2 192.168.1.0/24 [110/200] via 172.16.255.9, 00:02:59, Serial1/0 (也繞遠了,不直接通過R1走)
R5#
6、我們看到R5到10.0.0.0/8和192.168.1.0/24都是繞了個大圈通過ospf 區域來走,那它為什麼不直接通過R1這一跳來走呢。這樣路徑更近,隻要通過R1一個路由器轉發就行啊。呵呵!這是因為R5認為R2重分發過進來路由的管理距離是110。rip是120,走ospf更短。是以不選擇R1走,而是走R4。看來管理距離決定着路由器選擇那個路由協定的路徑過去。是以在這種情況之後。我們要去手動地在R5上修改到達R1的管理距離,強制讓它選擇最佳路由走R1。
7、我們可以通過一個acl加指定鍊路的distance來做:
R5(config)#access-list 1 permit 10.0.0.0 0.255.255.255(建立一個對目的網絡的通路控制清單)
R5(config)#router rip
R5(config-router)#distance 85 192.168.2.0 0.0.0.255 1(定義到R1的管理距離為85比對access-list1)
8、我們來看一下access-list 1:
R5#show access-lists 1
Standard IP access list 1
10 ermit 10.0.0.0, wildcard bits 0.255.255.255 (1 match) 已經有1個比對了
9、看一下R5 的路由表:
O 172.16.255.0 [110/192] via 172.16.255.9, 02:32:03, Serial1/0
O 172.16.255.4 [110/128] via 172.16.255.9, 02:32:03, Serial1/0
R 10.0.0.0/8 [85/1] via 192.168.2.1, 00:00:11, FastEthernet0/0 (現在變成R了,并且走R1了)
O E2 192.168.1.0/24 [110/200] via 172.16.255.9, 00:09:57, Serial1/0(這條路徑加一條ACL就能改到走R1了,那樣将會變成R不會是O E2)
10
R2#sh ip route
C 172.16.255.0 is directly connected, Serial1/1
O 172.16.255.4 [110/128] via 172.16.255.2, 02:46:52, Serial1/1
O 172.16.255.8 [110/192] via 172.16.255.2, 02:46:52, Serial1/1
O E1 10.0.0.0/8 [110/392] via 172.16.255.2, 00:15:01, Serial1/1
C 192.168.1.0/24 is directly connected, Serial1/0
O E1 192.168.2.0/24 [110/392] via 172.16.255.2, 02:46:52, Serial1/1
R2#
11、這次我來把兩條都改掉管理距離讓它們走R1:
R2(config)#access-list 1 permit 10.0.0.0 0.0.0.255 (建立第一個到目的網絡的通路控制清單)
R2(config)#access-list 1 permit 192.168.2.0 0.0.0.255(建立第二個到目的網絡的通路控制清單)
R2(config)#router rip
R2(config-router)#distance 85 192.168.1.1 0.0.0.0 1 (設定到R1的管理距離)
12、再來看一下R2的route:
R2(config-router)#do sho ip route
O 172.16.255.4 [110/128] via 172.16.255.2, 04:12:19, Serial1/1
O 172.16.255.8 [110/192] via 172.16.255.2, 04:12:19, Serial1/1
R 10.0.0.0/8 [85/1] via 192.168.1.1, 00:00:18, Serial1/0
R 192.168.2.0/24 [85/1] via 192.168.1.1, 00:00:18, Serial1/0
兩條都變成R了,都通過R1到目的網段。不會走ospf網絡。
本文轉自wxs-163 51CTO部落格,原文連結:http://blog.51cto.com/supercisco/251983