CCNA实验：默认路由配置

预配置

第一步：R1上的预配置

R1(config)#int s1/2

R1(config-if)#ip address 10.1.1.1 255.255.255.0

R1(config-if)#no sh

R1(config)#int lo0

R1(config-if)#ip ad 1.1.1.1 255.255.255.0

第二步：R2上的预配置

R2(config)#int s2/1

R2(config-if)#ip address 10.1.1.1 255.255.255.0

R2(config-if)#no sh

R2(config)#int lo0

R2(config-if)#ip address 2.2.2.2 255.255.255.0

---

实验过程：

第一步：先在R1上ping 2.2.2.2网段

R1#ping 2.2.2.2

Type escape sequence to abort.

Sending 5, 100-byte ICMP Echos to 2.2.2.2, timeout is 2 seconds:

.....

Success rate is 0 percent (0/5) （没有成功）

因为在R1上没有去2.2.2.0网段的路由

R1#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, * - candidate default

U - per-user static route, o - ODR

T - traffic engineered route

Gateway of last resort is not set

1.0.0.0/24 is subnetted, 1 subnets

C 1.1.1.0 is directly connected, Loopback0

10.0.0.0/24 is subnetted, 1 subnets

C 10.1.1.0 is directly connected, Serial1/2

R1#

可以看到没有去R2的路由

第二步：新增路由

在R1上加一条默认路由

R1(config)#ip route 0.0.0.0 0.0.0.0 10.1.1.2 （这里是下一条的地址或为出接口）

R1#show 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, * - candidate default

U - per-user static route, o - ODR

T - traffic engineered route

Gateway of last resort is 10.1.1.2 to network 0.0.0.0

1.0.0.0/24 is subnetted, 1 subnets

C 1.1.1.0 is directly connected, Loopback0

10.0.0.0/24 is subnetted, 1 subnets

C 10.1.1.0 is directly connected, Serial1/2

*S 0.0.0.0/0 [1/0] via 10.1.1.2 （这里可以看到多了一条默认路由）**

第四步：在R2上也加入一条默认路由让数据包能返回

R2(config)#ip route 0.0.0.0 0.0.0.0 s2/1

第五步：现在再次ping 测试一下

R1#ping 2.2.2.2

Type escape sequence to abort.

Sending 5, 100-byte ICMP Echos to 2.2.2.2, timeout is 2 seconds:

!!!!!

Success rate is 100 percent (5/5), round-trip min/avg/max = 12/20/40 ms

---

在实际环境中一般当路由器作为出口进，配置一条

ip route 0.0.0.0 0.0.0.0 x.x.x.x（x.x.x.x为运营商给的网关）

或者

ip route 0.0.0.0 0.0.0.0 f0/0（f0/0为去运营商的出接口）