A dynamic routing Introduction
1. Dynamic routing means : Routers use routing protocols to learn the network and update the routing tables.
2. Routing protocol classification
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3. Introduction administrative distance
for managing a distance (AD) determines the reliability of the route selection information received from neighboring routers, which is an integer of 0-255, and 0 represents the maximum reliability, mean that he will not have 255 data stream using a respective routing
default line distance (Show ip protocols view of the AD value of the dynamic routing)
| Source Routing | The default AD |
|---|---|
| Straight connector | 0 |
| Static Routing | 1 |
| External BGP | 20 |
| EIGRP | 90 |
| OSPF | 110 |
| RIP | 120 |
4. metric
measure is the routing protocol to route cost value assigned to the remote network
metric IP routing protocols are as follows:
| metric | routing |
|---|---|
| Broadband | EIGRP |
| Spending | OSPF |
| delay | EIGRP |
| Hops | RIP |
| load | EIGRP |
| reliability | EIGRP |
5.收敛
路由器收敛完成
-当所有路由表包含相同网络信息
当路由器继续交换路由信息
-当无信息时候收敛结束
-网络在到达收敛钱无法完全正常工作
6.距离矢量-路由环路
什么是路由环路？
路由环路是指数据包在一系列路由器之间不断传输却始终无法到达
其预期目的网络的一种现象
路由环路会造成的影响
环路内的路山器占用链路带宽来反复收发流量
路由器的CPU因不断循环数据包而不堪重负
影响到网络收敛
路由更新可能会失或无法得到及时处理
防环机制
定义最大度量以防止计数至无穷大
抑制计时器
水平分割
路由毒化或毒反转
触发更新
二.RIP路由信息的更新
1.RIP路由信息更新依托于时间周期的更新（更新周期为30秒）
当路由器A连接的网络拓扑发生改变后A路由器更新路由表，等到下一个发送周期通告更新后的路由表，路由器B收到此更新信息后更新自己的路由表
2.RIP配置
配置命令
router rip
network 分类网络 (network10.0.0.0network告诉路由协议RIP该通告哪些分类网络)
version 2
no auto-summary(关闭汇总)
See show ip route command
experimental environment below 
1 interfaces the router R2 and the RIP route ip address 
2. Set the same router R1 and R3
3. routing table show ip route
| Export | Explanation |
|---|---|
| R | Identify the source router RIP |
| 19.168.10.0 | Specify the remote network address |
| /24 | Change network subnet mask |
| [120/2] | Management distance 120; metric 2 |
| was 192.160.30.1 | Specify the next hop address to transmit data to a remote network |
| 00：00：28 | Specified amount of time since the last update route passes 28 seconds |
| FastEthernet0/0 | Specifies the local interface can reach remote networks |