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静态路由和默认路由

由 冷暖自知 提交于 2019-11-26 17:12:41

GNS3图标

不同网段之间可以通过路由器进行通信，但若是中间有多个路由器，在两三台的情况下，我们可以通过配置静态路由来实现数据转发。

实验拓扑

拓扑

使用两台路由器直连，每台下面再连接一台VPC。地址规划如下：

名称 接口 IP地址
R1 f0/0 192.168.30.1/24
R1 f0/1 192.168.10.1/24
R2 f0/0 192.168.30.2/24
R2 f0/1 192.168.20.1/24
PC1 e0 192.168.10.10/24
PC2 e0 192.168.20.10/24

静态路由

配置方法

全局模式下添加一条静态路由。

R1#configure terminal 
R1(config)#ip route 192.168.20.0 255.255.255.0 192.168.30.2
  • 192.168.20.0：目的网段
  • 255.255.255.0：子网掩码
  • 192.168.30.2：下一跳

配置过程

R1

  • 配置f0/1接口ip地址
R1#configure terminal 
R1(config)#interface fastEthernet 0/1
R1(config-if)#ip address 192.168.10.1 255.255.255.0
R1(config-if)#no shutdown 
R1(config-if)#exit
  • 配置f0/0接口ip地址
R1(config)#interface fastEthernet 0/0
R1(config-if)#ip address 192.168.30.1 255.255.255.0
R1(config-if)#no shutdown 
R1(config-if)#end
  • 查看接口地址及状态
R1#show ip interface brief 
Interface                  IP-Address      OK? Method Status                Protocol
FastEthernet0/0            192.168.30.1    YES manual up                    up      
FastEthernet0/1            192.168.10.1    YES manual up                    up
  • 查看路由表
R1#show 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

C    192.168.30.0/24 is directly connected, FastEthernet0/0
C    192.168.10.0/24 is directly connected, FastEthernet0/1
  • 添加到达192.168.20.0网段的静态路由
R1#configure terminal 
R1(config)#ip route 192.168.20.0 255.255.255.0 192.168.30.2
R1(config)#end
  • 再次查看路由表
R1#show 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

C    192.168.30.0/24 is directly connected, FastEthernet0/0
C    192.168.10.0/24 is directly connected, FastEthernet0/1
S    192.168.20.0/24 [1/0] via 192.168.30.2

R2

  • R2与R1的配置方法相同，以下为简写配置过程。
R2#conf t
R2(config)#int f0/1
R2(config-if)#ip add 192.168.20.1 255.255.255.0
R2(config-if)#no sh
R2(config-if)#int f0/0
R2(config-if)#ip add 192.168.30.2 255.255.255.0
R2(config-if)#no sh
R2(config-if)#ex
R2(config)#ip route 192.168.10.0 255.255.255.0 192.168.30.1
R2(config)#do show ip int b
Interface                  IP-Address      OK? Method Status                Protocol
FastEthernet0/0            192.168.30.2    YES manual up                    up      
FastEthernet0/1            192.168.20.1    YES manual up                    up      
R2(config)#do show 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

C    192.168.30.0/24 is directly connected, FastEthernet0/0
S    192.168.10.0/24 [1/0] via 192.168.30.1
C    192.168.20.0/24 is directly connected, FastEthernet0/1

PING 测试

配置 IP 地址

PC1> ip 192.168.10.10 255.255.255.0 192.168.10.1
Checking for duplicate address...
PC1 : 192.168.10.10 255.255.255.0 gateway 192.168.10.1
PC2> ip 192.168.20.10 192.168.20.1
Checking for duplicate address...
PC1 : 192.168.20.10 255.255.255.0 gateway 192.168.20.1

PING

PC1> ping 192.168.20.10 
192.168.20.10 icmp_seq=1 timeout
192.168.20.10 icmp_seq=2 timeout
84 bytes from 192.168.20.10 icmp_seq=3 ttl=62 time=41.947 ms
84 bytes from 192.168.20.10 icmp_seq=4 ttl=62 time=39.882 ms
84 bytes from 192.168.20.10 icmp_seq=5 ttl=62 time=42.885 ms
PC2> ping 192.168.10.10
84 bytes from 192.168.10.10 icmp_seq=1 ttl=62 time=38.025 ms
84 bytes from 192.168.10.10 icmp_seq=2 ttl=62 time=39.887 ms
84 bytes from 192.168.10.10 icmp_seq=3 ttl=62 time=43.782 ms
84 bytes from 192.168.10.10 icmp_seq=4 ttl=62 time=32.903 ms
84 bytes from 192.168.10.10 icmp_seq=5 ttl=62 time=38.942 ms

通过配置静态路由成功使不同网段之间互通。

默认路由

默认路由是一种特殊的静态路由，当配置了默认路由，转发数据包中目的地址在路由表中没有相匹配的表项时，数据包将按默认路由转发，否则数据包会被丢弃。

设想一：在R2上只配一条默认路由，是否可行？

设想二：R1和R2都只配一条默认路由，是否可行？

配置方法

全局模式下添加一条默认路由。

R2(config)#ip route 0.0.0.0 0.0.0.0 192.168.30.1
  • 0.0.0.0 0.0.0.0：代表任何网络
  • 192.168.30.1：下一跳

设想一

配置过程

  • R2删除添加的静态路由，添加默认路由。
R2(config)#no ip route 192.168.10.0 255.255.255.0
R2(config)#ip route 0.0.0.0 0.0.0.0 192.168.30.1
R2(config)#do show 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 192.168.30.1 to network 0.0.0.0

C    192.168.30.0/24 is directly connected, FastEthernet0/0
C    192.168.20.0/24 is directly connected, FastEthernet0/1
S*   0.0.0.0/0 [1/0] via 192.168.30.1

PING 测试

PC1> ping 192.168.20.10
192.168.20.10 icmp_seq=1 timeout
192.168.20.10 icmp_seq=2 timeout
84 bytes from 192.168.20.10 icmp_seq=3 ttl=62 time=37.905 ms
84 bytes from 192.168.20.10 icmp_seq=4 ttl=62 time=34.870 ms
84 bytes from 192.168.20.10 icmp_seq=5 ttl=62 time=42.728 ms
PC2> ping 192.168.10.10
84 bytes from 192.168.10.10 icmp_seq=1 ttl=62 time=38.995 ms
84 bytes from 192.168.10.10 icmp_seq=2 ttl=62 time=35.875 ms
84 bytes from 192.168.10.10 icmp_seq=3 ttl=62 time=36.911 ms
84 bytes from 192.168.10.10 icmp_seq=4 ttl=62 time=37.904 ms
84 bytes from 192.168.10.10 icmp_seq=5 ttl=62 time=35.912 ms

通过PING测试，发现是可行的。

设想二

配置过程

  • 再在R1上删除添加的静态路由，添加默认路由。
R1(config)#no ip route 192.168.20.0 255.255.255.0          
R1(config)#ip route 0.0.0.0 0.0.0.0 192.168.30.2           
R1(config)#do show 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 192.168.30.2 to network 0.0.0.0

C    192.168.30.0/24 is directly connected, FastEthernet0/0
C    192.168.10.0/24 is directly connected, FastEthernet0/1
S*   0.0.0.0/0 [1/0] via 192.168.30.2

PING 测试

PC1> ping 192.168.20.10
192.168.20.10 icmp_seq=1 timeout
192.168.20.10 icmp_seq=2 timeout
84 bytes from 192.168.20.10 icmp_seq=3 ttl=62 time=33.073 ms
84 bytes from 192.168.20.10 icmp_seq=4 ttl=62 time=36.042 ms
84 bytes from 192.168.20.10 icmp_seq=5 ttl=62 time=41.983 ms
PC2> ping 192.168.10.10
84 bytes from 192.168.10.10 icmp_seq=1 ttl=62 time=43.736 ms
84 bytes from 192.168.10.10 icmp_seq=2 ttl=62 time=42.030 ms
84 bytes from 192.168.10.10 icmp_seq=3 ttl=62 time=39.927 ms
84 bytes from 192.168.10.10 icmp_seq=4 ttl=62 time=34.038 ms
84 bytes from 192.168.10.10 icmp_seq=5 ttl=62 time=40.854 ms

好像也可以哦，没问题；若是不小心ping了一个不存在的地址呢？

PC1> ping 192.168.40.10
*192.168.30.2 icmp_seq=1 ttl=254 time=698.062 ms (ICMP type:11, code:0, TTL expired in transit)
*192.168.30.2 icmp_seq=2 ttl=254 time=705.060 ms (ICMP type:11, code:0, TTL expired in transit)
*192.168.30.2 icmp_seq=3 ttl=254 time=707.124 ms (ICMP type:11, code:0, TTL expired in transit)
*192.168.30.2 icmp_seq=4 ttl=254 time=702.108 ms (ICMP type:11, code:0, TTL expired in transit)
*192.168.30.2 icmp_seq=5 ttl=254 time=694.003 ms (ICMP type:11, code:0, TTL expired in transit)
PC2> ping 192.168.40.10   
*192.168.30.1 icmp_seq=1 ttl=254 time=700.994 ms (ICMP type:11, code:0, TTL expired in transit)
*192.168.30.1 icmp_seq=2 ttl=254 time=704.114 ms (ICMP type:11, code:0, TTL expired in transit)
*192.168.30.1 icmp_seq=3 ttl=254 time=698.020 ms (ICMP type:11, code:0, TTL expired in transit)
*192.168.30.1 icmp_seq=4 ttl=254 time=700.092 ms (ICMP type:11, code:0, TTL expired in transit)
*192.168.30.1 icmp_seq=5 ttl=254 time=694.289 ms (ICMP type:11, code:0, TTL expired in transit)

发现个问题，TTL传输中过期，说明数据包在两个路由器之间被互相转发，直到数据包TTL为0，这样势必会浪费路由器的资源，对正常的运作产生影响，所以这是不可行的。

最后

关于静态路由的相关实验到此结束，下一篇关于VLAN的实验。

标签
静态路由
默认路由
is-is
config
ospf
icmp
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