默认路由-白红宇

默认路由

默认路由是静态路由的一种特殊形式，可以用来跟位置望断通讯，但是运行环境只能在末梢网络的路由器上

在这个拓扑里面只有第一个和第三个路由器上才能配置默认路由而第二个路由器上只能配置静态路由

Ru1上的基本配置

Router>en

Router#conf t

Enter configuration commands, one per line. End with CNTL/Z.

Router(config)#host ru1

ru1(config)#int s0/0

ru1(config-if)#ip add 192.168.1.1 255.255.255.0

ru1(config-if)#clock rate 64000

ru1(config-if)#no shut

%LINK-5-CHANGED: Interface Serial0/0, changed state to down

ru1(config-if)#exit

ru1(config)#int f0/0

ru1(config-if)#ip add 172.16.1.1 255.255.255.0

ru1(config-if)#no shut

%LINK-5-CHANGED: Interface FastEthernet0/0, changed state to up

%LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/0, changed state to up

ru1(config-if)#exit

ru1(config)#

ru2 上的基本配置

Router>

Router>en

Router#conf t

Enter configuration commands, one per line. End with CNTL/Z.

Router(config)#host ru2

ru2(config)#int s0/0

ru2(config-if)#ip add 192.168.1.2 255.255.255.0

ru2(config-if)#no shut

%LINK-5-CHANGED: Interface Serial0/0, changed state to up

ru2(config-if)#

%LINEPROTO-5-UPDOWN: Line protocol on Interface Serial0/0, changed state to upexit

ru2(config)#int f0/0

ru2(config-if)#ip add 172.16.2.1 255.255.255.0

ru2(config-if)#no shut

%LINK-5-CHANGED: Interface FastEthernet0/0, changed state to up

%LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/0, changed state to up

ru2(config-if)#exit

ru2(config)#int s0/1

ru2(config-if)#ip add 192.168.2.1 255.255.255.0

ru2(config-if)#clock rate 64000

ru2(config-if)#no shut

ru2(config-if)#exit

ru2(config)#

ru3 上的基本配置

Router>en

Router#conf t

Enter configuration commands, one per line. End with CNTL/Z.

Router(config)#host ru3

ru3(config)#int s0/0

ru3(config-if)#ip add 192.168.2.2 255.255.255.0

ru3(config-if)#no shut

%LINK-5-CHANGED: Interface Serial0/0, changed state to up

ru3(config-if)#exit

ru3(config)#int

%LINEPROTO-5-UPDOWN: Line protocol on Interface Serial0/0, changed state to up f0/0

ru3(config-if)#ip add 172.16.3.1 255.255.255.0

ru3(config-if)#no shut

%LINK-5-CHANGED: Interface FastEthernet0/0, changed state to up

%LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/0, changed state to up

ru3(config-if)#exit

ru3(config)#

我们开始进行路由协议的配置了

ru1(config)#ip route 0.0.0.0 0.0.0.0 192.168.1.2

ru2(config)#ip route 172.16.1.0 255.255.255.0 192.168.1.1

ru2(config)#ip route 172.16.3.0 255.255.255.0 192.168.2.2

ru2(config)#

ru3(config)#ip route 0.0.0.0 0.0.0.0 192.168.2.1

这里呢一定要分清楚哪个是你的下一跳ip地址，注意一下ru1 和ru3 上的配置

ru3#sh ip route

Codes: C - connected, S - static, I - IGRP, 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, E - EGP

i - IS-IS, 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 192.168.2.1 to network 0.0.0.0

172.16.0.0/24 is subnetted, 1 subnets

C 172.16.3.0 is directly connected, FastEthernet0/0

C 192.168.2.0/24 is directly connected, Serial0/0

S* 0.0.0.0/0 [1/0] via 192.168.2.1

ru3#ping 172.16.1.1

Type escape sequence to abort.

Sending 5, 100-byte ICMP Echos to 172.16.1.1, timeout is 2 seconds:

!!!!!

Success rate is 100 percent (5/5), round-trip min/avg/max = 62/65/79 ms

ru3#ping 172.16.2.1

Type escape sequence to abort.

Sending 5, 100-byte ICMP Echos to 172.16.2.1, timeout is 2 seconds:

!!!!!

Success rate is 100 percent (5/5), round-trip min/avg/max = 31/34/47 ms

ru3#

上面的这个是在ru3 上查看到的路由表信息注意学到的末梢路由的标示

ru2#sh ip route

Codes: C - connected, S - static, I - IGRP, 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, E - EGP

i - IS-IS, 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

172.16.0.0/24 is subnetted, 3 subnets

S 172.16.1.0 [1/0] via 192.168.1.1

C 172.16.2.0 is directly connected, FastEthernet0/0

S 172.16.3.0 [1/0] via 192.168.2.2

C 192.168.1.0/24 is directly connected, Serial0/0

C 192.168.2.0/24 is directly connected, Serial0/1

ru2#

这是ru2上学到的路由信息其中C表示的是直连网段 S 表示静态路由 S* 表示的是缺省路由即我们说的默认路由

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我三台pc机的ip

依次是172.16.1.2 172.16.2.2 172.16.3.2

这是在pc3 上的查勘信息

以及测试与其他计算机的连通情况

Packet Tracer PC Command Line 1.0

PC>ipconfig

IP Address......................: 172.16.3.2

Subnet Mask.....................: 255.255.0.0

Default Gateway.................: 172.16.3.1

PC>ping 172.16.1.2

Pinging 172.16.1.2 with 32 bytes of data:

Request timed out.

Reply from 172.16.1.2: bytes=32 time=125ms TTL=125

Reply from 172.16.1.2: bytes=32 time=109ms TTL=125

Reply from 172.16.1.2: bytes=32 time=125ms TTL=125

Ping statistics for 172.16.1.2:

Packets: Sent = 4, Received = 3, Lost = 1 (25% loss),

Approximate round trip times in milli-seconds:

Minimum = 109ms, Maximum = 125ms, Average = 119ms

PC>ping 172.16.2.2

Pinging 172.16.2.2 with 32 bytes of data:

Request timed out.

Reply from 172.16.2.2: bytes=32 time=125ms TTL=126

Reply from 172.16.2.2: bytes=32 time=78ms TTL=126

Reply from 172.16.2.2: bytes=32 time=94ms TTL=126

Ping statistics for 172.16.2.2:

Packets: Sent = 4, Received = 3, Lost = 1 (25% loss),

Approximate round trip times in milli-seconds:

Minimum = 78ms, Maximum = 125ms, Average = 99ms

PC>

静态路由协议的特点

对路由器cpu没有管理性开销

在路由器急案没有带宽占用

增加了安全性，

缺点就是必须对网络有足够的了解，对于大型的网络配置繁琐，对于一个稍微大点的网络来说配置的工作量复杂，且容易出错

本文转自 yuzeying1 51CTO博客，原文链接:http://blog.51cto.com/yuzeying/178227