RIP 的防环机制共有6种：
1.最大跳数
竞选团支书发言稿2.水平分割
3.毒化路由
4.毒性逆转
5.hold-down计时器
6.触发更新
联想：定时更新和触发更新的区别：
电算化会计信息系统•定时更新：运行如RIP，IGRP等距离矢量协议的路由器以一定的时间间隔广播路由表的全部内容。
RIP缺省情况下每隔30s向每个活跃接口广播所有路由。IGRP的缺省更新时间间隔是90s。
触发更新：更新通过在网络发生变化时为等待到定时更新的时间点就立即发送更新，从而消除了定时更新带来的收敛延迟，快速更新发生在网络的结点和结点之间，减少了整个网络的收敛时间。
以下针对每种更新方式，以实验的方式进行验证：
l最大跳数演示试验：
R1上有一个环回口地址1.1.1.1/24位，全网起RIP V2协议，演示醉倒跳数的试验。
R1R2R3
router rip
version 2
network 1.0.0.0 network 10.0.0.0 network 172.16.0.0 no auto-summary router rip
version 2
network 10.0.0.0
no auto-summary
router rip
version 2
network 10.0.0.0
network 172.16.0.0
no auto-summary
R2#show ip route rip
1.0.0.0/24 is subnetted, 1 subnets
R 1.1.1.0 [120/1] via 10.1.12.1, 00:00:06, Serial1/0
172.16.0.0/24 is subnetted, 1 subnets
R 172.16.1.0 [120/1] via 10.1.23.3, 00:00:21, Serial1/1
[120/1] via 10.1.12.1, 00:00:26, Serial1/0
10.0.0.0/8 is variably subnetted, 4 subnets, 3 masks
R 10.1.45.1/32 [120/1] via 10.1.12.1, 00:00:26, Serial1/0
R 10.1.34.0/26 [120/1] via 10.1.12.1, 00:00:26, Serial1/0
R3#show ip route rip
1.0.0.0/24 is subnetted, 1 subnets
R 1.1.1.0 [120/1] via 172.16.1.1, 00:00:06, FastEthernet0/0
10.0.0.0/8 is variably subnetted, 4 subnets, 3 masks
R 10.1.12.0/24 [120/1] via 10.1.23.2, 00:00:06, Serial1/0
[120/1] via 172.16.1.1, 00:00:06, FastEthernet0/0
R 10.1.45.1/32 [120/1] via 172.16.1.1, 00:00:06, FastEthernet0/0
R 10.1.34.0/26 [120/1] via 172.16.1.1, 00:00:06, FastEthernet0/0
正常情况下R2的下一跳是R1的串口地址，R3的下一跳是R1的以太口地址。
第一步：被动接口 R1的以太网口R1(config-router)#pass fa0/0
大约4分钟后，R3上看到的1.1.1.0/24的下一跳是R2过来的。
R3#show ip route rip
1.0.0.0/24 is subnetted, 1 subnets
R 1.1.1.0 [120/2] via 10.1.23.2, 00:00:06, Serial1/0
10.0.0.0/8 is variably subnetted, 4 subnets, 3 masks
R 10.1.12.0/24 [120/1] via 10.1.23.2, 00:00:06, Serial1/0
R 10.1.45.1/32 [120/2] via 10.1.23.2, 00:00:06, Serial1/0
R 10.1.34.0/26 [120/2] via 10.1.23.2, 00:00:06, Serial1/0
第二步：把R1的s1/1的接口也被动掉，且断开lookback0接口。且打开个各个路由器的debug ip rip
R1(config)#router rip
R1(config-router)#passive-interface s1/1
R1(config)#int loopback 0
R1(config-if)#shutdown
第三步：直到R1收到1.1.1.0的下一跳是R2时，打开s1/1的被动接口。
R1(config-router)#do show ip route rip
1.0.0.0/24 is subnetted, 1 subnets
R 1.1.1.0 [120/3] via 172.16.1.3, 00:00:02, FastEthernet0/0
Jun 28 20:06:28.875: RIP: received v2 update from 10.1.12.2 on Serial1/1
*Jun 28 20:06:28.879: 10.1.23.0/24 via 0.0.0.0 in 1 hops
R1(config-router)#no pas s1/1
R1(config-router)#
*Jun 28 20:06:32.955: RIP: received v2 update from 172.16.1.3 on FastEthernet0/0 *Jun 28 20:06:32.959: 1.1.1.0/24 via 0.0.0.0 in 3 hops
*Jun 28 20:06:32.959: 10.1.12.0/24 via 0.0.0.0 in 2 hops
*Jun 28 20:06:32.959: 10.1.23.0/24 via 0.0.0.0 in 1 hops
*Jun 28 20:06:32.959: 10.1.34.0/26 via 0.0.0.0 in 3 hops
*Jun 28 20:06:32.959: 10.1.45.1/32 via 0.0.0.0 in 3 hops
R1(config-router)#
*Jun 28 20:06:35.219: RIP: nding v2 update to 224.0.0.9 via Loopback2 (10.1.23.2)
*Jun 28 20:06:35.219: RIP: build update entries
*Jun 28 20:06:35.219: 1.1.1.0/24 via 0.0.0.0, metric 4, tag 0
*Jun 28 20:06:35.219: 10.1.12.0/24 via 0.0.0.0, metric 1, tag 0
*Jun 28 20:06:35.219: 10.1.34.0/26 via 0.0.0.0, metric 1, tag 0
*Jun 28 20:06:35.219: 10.1.45.1/32 via 0.0.0.0, metric 1, tag 0
*Jun 28 20:06:35.219: 172.16.1.0/24 via 0.0.0.0, metric 1, tag 0
*Jun 28 20:06:35.219: RIP: ignored v2 packet from 10.1.23.2 (sourced from one of our address)
R1(config-router)#
轮廓的意思*Jun 28 20:06:39.027: RIP: nding v2 update to 224.0.0.9 via Loopback3 (10.1.34.1)
*Jun 28 20:06:39.027: RIP: build update entries
*Jun 28 20:06:39.031: 1.1.1.0/24 via 0.0.0.0, metric 4, tag 0
*Jun 28 20:06:39.031: 10.1.12.0/24 via 0.0.0.0, metric 1, tag 0
*Jun 28 20:06:39.035: 10.1.23.0/24 via 0.0.0.0, metric 1, tag 0
*Jun 28 20:06:39.035: 10.1.45.1/32 via 0.0.0.0, metric 1, tag 0
*Jun 28 20:06:39.035: 172.16.1.0/24 via 0.0.0.0, metric 1, tag 0
*Jun 28 20:06:39.035: RIP: ignored v2 packet from 10.1.34.1 (sourced from one of our address)
R1(config-router)#
*Jun 28 20:06:40.519: RIP: nding v2 update to 224.0.0.9 via Loopback4 (10.1.45.1)
*Jun 28 20:06:40.519: RIP: build update entries
*Jun 28 20:06:40.519: 1.1.1.0/24 via 0.0.0.0, metric 4, tag 0
*Jun 28 20:06:40.519: 10.1.12.0/24 via 0.0.0.0, metric 1, tag 0
*Jun 28 20:06:40.519: 10.1.23.0/24 via 0.0.0.0, metric 1, tag 0
*Jun 28 20:06:40.519: 10.1.34.0/26 via 0.0.0.0, metric 1, tag 0
*Jun 28 20:06:40.519: 172.16.1.0/24 via 0.0.0.0, metric 1, tag 0
*Jun 28 20:06:40.519: RIP: ignored v2 packet from 10.1.45.1 (sourced from one of our address)
R1(config-router)#
*Jun 28 20:06:41.679: RIP: nding v2 update to 224.0.0.9 via Serial1/1 (10.1.12.1)
*Jun 28 20:06:41.679: RIP: build update entries
*Jun 28 20:06:41.683: 1.1.1.0/24 via 0.0.0.0, metric 4, tag 0
*Jun 28 20:06:41.683: 10.1.23.0/24 via 0.0.0.0, metric 1, tag 0
*Jun 28 20:06:41.687: 10.1.34.0/26 via 0.0.0.0, metric 1, tag 0
*Jun 28 20:06:41.687: 10.1.45.1/32 via 0.0.0.0, metric 1, tag 0
*Jun 28 20:06:41.691: 172.16.1.0/24 via 0.0.0.0, metric 1, tag 0
R1(config-router)#
expert
*Jun 28 20:06:45.711: RIP: received v2 update from 172.16.1.3 on FastEthernet0/0 *Jun 28 20:06:45.715: 1.1.1.0/24 via 0.0.0.0 in 6 hops
R1(config-router)#
*Jun 28 20:06:47.715: RIP: nding v2 flash update to 224.0.0.9 via Serial1/1 (10.1.12.1)
*Jun 28 20:06:47.715: RIP: build flash update entries
*Jun 28 20:06:47.719: 1.1.1.0/24 via 0.0.0.0, metric 7, tag 0
*Jun 28 20:06:47.719: RIP: nding v2 flash update to 224.0.0.9 via Loopback2 (10.1.23.2)
*Jun 28 20:06:47.723: RIP: build flash update entries
*Jun 28 20:06:47.723: 1.1.1.0/24 via 0.0.0.0, metric 7, tag 0
*Jun 28 20:06:47.727: RIP: nding v2 flash update to 224.0.0.9 via Loopback3 (10.1.34.1)
*Jun 28 20:06:47.727: RIP: build flash update entries
*Jun 28 20:06:47.727: 1.1.1.0/24 via 0.0.0.0, metric 7, tag 0
R1(config-router)#
*Jun 28 20:06:47.731: RIP: nding v2 flash update to 224.0.0.9 via Loopback4 (10.1.45.1)
*Jun 28 20:06:47.735: RIP: build flash update entries
*Jun 28 20:06:47.735: 1.1.1.0/24 via 0.0.0.0, metric 7, tag 0
*Jun 28 20:06:47.747: RIP: ignored v2 packet from 10.1.23.2 (sourced from one of our address)
*Jun 28 20:06:47.751: RIP: ignored v2 packet from 10.1.34.1 (sourced from one of our address)
*Jun 28 20:06:47.751: RIP: ignored v2 packet from 10.1.45.1 (sourced from one of our address)
R1(config-router)#
*Jun 28 20:06:51.747: RIP: received v2 update from 172.16.1.3 on FastEthernet0/0 *Jun 28 20:06:51.751: 1.1.1.0/24 via 0.0.0.0 in 9 hops
R1(config-router)#
*Jun 28 20:06:53.751: RIP: nding v2 flash update to 224.0.0.9 via Serial1/1 (10.1.12.1)
*Jun 28 20:06:53.751: RIP: build flash update entries
*Jun 28 20:06:53.751: 1.1.1.0/24 via 0.0.0.0, metric 10, tag 0
*Jun 28 20:06:53.751: RIP: nding v2 flash update to 224.0.0.9 via Loopback2 (10.1.23.2)enhanced是什么意思
*Jun 28 20:06:53.751: RIP: build flash update entries
*Jun 28 20:06:53.751: 1.1.1.0/24 via 0.0.0.0, metric 10, tag 0
*Jun 28 20:06:53.751: RIP: nding v2 flash update to 224.0.0.9 via Loopback3 (10.1.34.1)
*Jun 28 20:06:53.751: RIP: build flash update entries
*Jun 28 20:06:53.751: 1.1.1.0/24 via 0.0.0.0, metric 10, tag 0
R1(config-router)#
*Jun 28 20:06:53.751: RIP: nding v2 flash update to 224.0.0.9 via Loopback4 (10.1.45.1)
*Jun 28 20:06:53.751: RIP: build flash update entries
*Jun 28 20:06:53.751: 1.1.1.0/24 via 0.0.0.0, metric 10, tag 0
*Jun 28 20:06:53.751: RIP: ignored v2 packet from 10.1.23.2 (sourced from one of our address)
秘密的英文*Jun 28 20:06:53.751: RIP: ignored v2 packet from 10.1.34.1 (sourced from one of our address)
*Jun 28 20:06:53.751: RIP: ignored v2 packet from 10.1.45.1 (sourced from one of our address)
武汉口译培训R1(config-router)#
*Jun 28 20:06:56.387: RIP: received v2 update from 10.1.12.2 on Serial1/1
*Jun 28 20:06:56.391: 10.1.23.0/24 via 0.0.0.0 in 1 hops
R1(config-router)#
*Jun 28 20:06:57.735: RIP: received v2 update from 172.16.1.3 on FastEthernet0/0 *Jun 28 20:06:57.735: 1.1.1.0/24 via 0.0.0.0 in 12 hops
R1(config-router)#
*Jun 28 20:06:59.739: RIP: nding v2 flash update to 224.0.0.9 via Serial1/1 (10.1.12.1)
*Jun 28 20:06:59.739: RIP: build flash update entries
*Jun 28 20:06:59.743: 1.1.1.0/24 via 0.0.0.0, metric 13, tag 0
*Jun 28 20:06:59.743: RIP: nding v2 flash update to 224.0.0.9 via Loopback2 (10.1.23.2)
*Jun 28 20:06:59.747: RIP: build flash update entries
*Jun 28 20:06:59.747: 1.1.1.0/24 via 0.0.0.0, metric 13, tag 0
*Jun 28 20:06:59.751: RIP: nding v2 flash update to 224.0.0.9 via Loopback3 (10.1.34.1)
*Jun 28 20:06:59.751: RIP: build flash update entries
*Jun 28 20:06:59.751: 1.1.1.0/24 via 0.0.0.0, metric 13, tag 0
R1(config-router)#
*Jun 28 20:06:59.751: RIP: nding v2 flash update to 224.0.0.9 via Loopback4 (10.1.45.1)
*Jun 28 20:06:59.751: RIP: build flash update entries
*Jun 28 20:06:59.751: 1.1.1.0/24 via 0.0.0.0, metric 13, tag 0
*Jun 28 20:06:59.751: RIP: ignored v2 packet from 10.1.23.2 (sourced from one of our address)
*Jun 28 20:06:59.751: RIP: ignored v2 packet from 10.1.34.1 (sourced from one of our address)
*Jun 28 20:06:59.751: RIP: ignored v2 packet from 10.1.45.1 (sourced from one of our address)
give it a go
R1(config-router)#
*Jun 28 20:07:02.411: RIP: received v2 update from 172.16.1.3 on FastEthernet0/0 *Jun 28 20:07:02.415: 1.1.1.0/24 via 0.0.0.0 in 15 hops
*Jun 28 20:07:02.415: 10.1.12.0/24 via 0.0.0.0 in 2 hops
*Jun 28 20:07:02.415: 10.1.23.0/24 via 0.0.0.0 in 1 hops
*Jun 28 20:07:02.415: 10.1.34.0/26 via 0.0.0.0 in 3 hops
*Jun 28 20:07:02.415: 10.1.45.1/32 via 0.0.0.0 in 3 hops
*Jun 28 20:07:03.207: RIP: nding v2 update to 224.0.0.9 via Loopback2 (10.1.23.2)
*Jun 28 20:07:03.207: RIP: build update entries
*Jun 28 20:07:03.207: 1.1.1.0/24 via 0.0.0.0, metric 16, tag 0
*Jun 28 20:07:03.207: 10.1.12.0/24 via 0.0.0.0, metric 1, tag 0
R1(config-router)#
*Jun 28 20:07:03.207: 10.1.34.0/26 via 0.0.0.0, metric 1, tag 0
*Jun 28 20:07:03.207: 10.1.45.1/32 via 0.0.0.0, metric 1, tag 0
韩语入门*Jun 28 20:07:03.207: 172.16.1.0/24 via 0.0.0.0, metric 1, tag 0
*Jun 28 20:07:03.211: RIP: ignored v2 packet from 10.1.23.2 (sourced from one of our address)
*Jun 28 20:07:03.719: RIP: received v2 update from 172.16.1.3 on FastEthernet0/0 *Jun 28 20:07:03.723: 1.1.1.0/24 via 0.0.0.0 in 15 hops
休息日*Jun 28 20:07:04.415: RIP: nding v2 flash update to 224.0.0.9 via Serial1/1 (10.1.12.1)
*Jun 28 20:07:04.415: RIP: build flash update entries
*Jun 28 20:07:04.419: 1.1.1.0/24 via 0.0.0.0, metric 16, tag 0
*Jun 28 20:07:04.419: RIP: nding v2 flash update to 224.0.0.9 via Loopback2 (10.1.23.2)
*Jun 28 20:07:04.423: RIP: build flash update entries
*Jun 28 20:07:04.423: 1.1.1.0/24 via 0.0.0.0, metric 16, tag 0
*Jun 28 20:07:04.427: RIP: nding v2 flash update to 224.0.0.9 via Loopback3 (10.1.34.1)
*Jun 28 20:07:04.427: RIP: build flash updat
R1(config-router)#e entries
*Jun 28 20:07:04.427: 1.1.1.0/24 via 0.0.0.0, metric 16, tag 0
*Jun 28 20:07:04.431: RIP: nding v2 flash update to 224.0.0.9 via Loopback4 (10.1.45.1)
*Jun 28 20:07:04.431: RIP: build flash update entries
*Jun 28 20:07:04.431: 1.1.1.0/24 via 0.0.0.0, metric 16, tag 0
*Jun 28 20:07:04.431: RIP: ignored v2 packet from 10.1.23.2 (sourced from one of our address)
*Jun 28 20:07:04.431: RIP: ignored v2 packet from 10.1.34.1 (sourced from one of our address)
*Jun 28 20:07:04.431: RIP: ignored v2 packet from 10.1.45.1 (sourced from one of our address)
R1(config-router)#
*Jun 28 20:07:06.411: RIP: received v2 update from 10.1.12.2 on Serial1/1
*Jun 28 20:07:06.415: 1.1.1.0/24 via 0.0.0.0 in 16 hops (inaccessible) R1(config-router)#
