一、拓撲圖:
二、IBGP鄰居學來的資訊,不會傳遞給另外的IBGP鄰居,需要再去手動指定鄰居,BGP這條路徑能不能通,要看這條路徑否成為最佳路徑和下一跳是否正确與可達:
1、配置各路由器的IP位址以及配置BGP協定。現在來看一下R3的路由表,看到R3能學到全網的路由:
3、再去R4上看一下R4的路由表發現沒有學到10.1.255.0/30和130.130.1.0/24這兩條路由:
8、但我在R4上traceroute 10.1.255.4之後,發現R4的路由表發生了變化10.1.255.0/30 不存在了。
R4#traceroute 10.1.255.4
Type escape sequence to abort.
Tracing the route to 10.1.255.4
1 10.1.255.9 52 msec 32 msec 16 msec
2 * * *
3 * * *
4 * * *
R4#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
10.0.0.0/30 is subnetted, 3 subnets
B 10.1.255.4 [200/0] via 10.1.255.9, 00:00:24
C 10.1.255.12 is directly connected, Serial1/1
C 10.1.255.8 is directly connected, Serial1/0
150.150.0.0/24 is subnetted, 1 subnets
B 150.150.1.0 [20/0] via 10.1.255.14, 00:23:42
R4#ping 10.1.255.4
Sending 5, 100-byte ICMP Echos to 10.1.255.4, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 4/26/52 ms
R4#
(超過8萬字一篇發不了。待續,請接着看下篇)
B 10.1.255.4 [200/0] via 10.1.255.9, 00:00:21
B 150.150.1.0 [20/0] via 10.1.255.14, 00:02:27
4、終其原因是因為:IBGP對等體學習到的路由,是不會向其它的IBGP對等體通告的。拓撲中的R3從IBGP對等體R4學來的路由是不會向R2這個IBGP對等體通告,同理R3從R2學來的路由也不會向R4通告。是以就造成了R2和R4學不到完整的路由資訊。
5、先在R2和R4上互指IBGP鄰居,一定要互指,不然鄰居不能完全建立起來:
R2(config)#router bgp 64513
R2(config-router)#nei 10.1.255.10 remote 64513
R4(config)#router bgp 64513
R4(config-router)#nei 10.1.255.5 remote 64513
6、互相指定完IBGP鄰居之後,用clear ip bgp * 把路由表涮新一下。然後再來看一下R2和R4的路由表:
R2#sh ip route
10.0.0.0/30 is subnetted, 4 subnets
C 10.1.255.4 is directly connected, Serial1/1
C 10.1.255.0 is directly connected, Serial1/0
B 10.1.255.12 [200/0] via 10.1.255.10, 00:00:47
B 10.1.255.8 [200/0] via 10.1.255.6, 00:00:56
130.130.0.0/24 is subnetted, 1 subnets
B 130.130.1.0 [20/0] via 10.1.255.1, 00:00:45
B 150.150.1.0 [200/0] via 10.1.255.14, 00:00:24
R2#
B 10.1.255.4 [200/0] via 10.1.255.5, 00:00:11
B 10.1.255.0 [200/0] via 10.1.255.5, 00:00:11
B 150.150.1.0 [20/0] via 10.1.255.14, 00:05:26
7、通過互指鄰居,發現R2能學到全網的路由但是R4卻不能學到130.130.1.0/24這條路由,而且還發現到10.1.255.4與10.1.255.0 走的都是10.1.255.5。
..... (發現不通)
Success rate is 0 percent (0/5)
R3#sh ip route
C 10.1.255.4 is directly connected, Serial1/0
B 10.1.255.0 [200/0] via 10.1.255.5, 00:07:05
B 10.1.255.12 [200/0] via 10.1.255.10, 00:06:59
C 10.1.255.8 is directly connected, Serial1/1
B 130.130.1.0 [200/0] via 10.1.255.1, 00:06:50
B 150.150.1.0 [200/0] via 10.1.255.14, 00:06:29
2、去看一下R2的路由表,發現R2沒有學到10.1.255.12/24和150.150.1.0/24這兩條路由:
B 10.1.255.8 [200/0] via 10.1.255.6, 00:01:16
B 130.130.1.0 [20/0] via 10.1.255.1, 00:00:46
本文轉自wxs-163 51CTO部落格,原文連結:http://blog.51cto.com/supercisco/268201