实验目标：
基本配置
R1
! hostname R1 ! no ip domain lookup ! interface Serial1/0 ip address 12.1.1.1 255.255.255.0 ! ip classless ! line con 0 exec-timeout 0 0 logging synchronous !
R2
! hostname R2 ! no ip domain lookup ! interface Loopback0 ip address 2.3.3.3 255.255.255.0 secondary ip address 3.3.3.3 255.255.255.0 secondary ip address 2.1.1.1 255.255.255.0 secondary ip address 2.2.2.2 255.255.255.0 ! interface Serial2/0 ip address 12.1.1.2 255.255.255.0 ! ip classless ! line con 0 exec-timeout 0 0 logging synchronous !
如上配置，已经将基本的地址信息配置完成，下面将配置静态路由
R1(config)#ip route 0.0.0.0 0.0.0.0 s1/0 12.1.1.2 默认路由
R1(config)#ip route 2.2.2.0 255.255.255.0 s1/0 12.1.1.2
第一无类查找
批注：路由器接口默认是无类路由
ip classless (无类)
验证：
R1#show ip route
2.0.0.0/24 is subnetted, 1 subnets
S 2.2.2.0 [1/0] via 12.1.1.2, Serial1/0
12.0.0.0/24 is subnetted, 1 subnets
C 12.1.1.0 is directly connected, Serial1/0
S* 0.0.0.0/0 [1/0] via 12.1.1.2, Serial1/0
R2#show ip route
2.0.0.0/24 is subnetted, 3 subnets
C 2.1.1.0 is directly connected, Loopback0
C 2.2.2.0 is directly connected, Loopback0
C 2.3.3.0 is directly connected, Loopback0
3.0.0.0/24 is subnetted,1subnets
C 3.3.3.0 is directly connected, Loopback0
12.0.0.0/24 is subnetted, 1 subnets
C 12.1.1.0 is directly connected, Serial1/1
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 = 24/43/76 ms
R1#ping 2.1.1.1
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 (0/5), round-trip min/avg/max = 24/43/76 ms
R1#ping 2.3.3.3
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 = 24/43/76 ms
R1#ping 3.3.3.3
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 = 24/43/76 ms
第二有类查找
批注：路由器接口默认是无类路由，所以应将路由器改为有类
no ip classless（有类）
R1(config)#no ip classless
R2(config)#no ip classless
验证：
R1#show ip route
2.0.0.0/24 is subnetted, 1 subnets
S 2.2.2.0 [1/0] via 12.1.1.2, Serial1/0
12.0.0.0/24 is subnetted, 1 subnets
C 12.1.1.0 is directly connected, Serial1/0
S* 0.0.0.0/0 [1/0] via 12.1.1.2, Serial1/0
R2#show ip route
2.0.0.0/24 is subnetted, 3 subnets
C 2.1.1.0 is directly connected, Loopback0
C 2.2.2.0 is directly connected, Loopback0
C 2.3.3.0 is directly connected, Loopback0
3.0.0.0/24 is subnetted, 1 subnets
C 3.3.3.0 is directly connected, Loopback0
12.0.0.0/24 is subnetted, 1 subnets
C 12.1.1.0 is directly connected, Serial1/1
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 = 24/43/76 ms
R1#ping 2.1.1.1
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 (0/5), round-trip min/avg/max = 24/43/76 ms
R1#ping 2.3.3.3
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 = 24/43/76 ms
R1#ping 3.3.3.3
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 = 24/43/76 ms
按照无类路由的查找原则从R1 ，ping R2上环回口都应该是通的，反观有类路由，只有ping R2上的环回口2.2.2.2 和3.3.3.3是通的。因为按照有类路由的查找原则，首先看该路由是否有类路由，是有类路由，再去匹配主网位，不匹配，再去匹配默认路由，默认路由匹配转发，默认路由不匹配丢弃，反观如主网位匹配，再匹配子网位，子网位匹配转发，子网位不匹配丢弃。具体路径参照下图：
