R1#show ip route Gateway of last resort is 0.0.0.0 to network 0.0.0.0 C 192.168.12.0/24 is directly connected, Ethernet0/0 1.0.0.0/32 is subnetted, 1 subnets C 1.1.1.1 is directly connected, Loopback0 D 192.168.23.0/24 [90/307200] via 192.168.12.2, 00:03:47, Ethernet0/0 S* 0.0.0.0/0 is directly connected, Null0
R3#sh ip route Gateway of last resort is 192.168.23.2 to network 0.0.0.0 D 192.168.12.0/24 [90/307200] via 192.168.23.2, 00:05:29, Ethernet0/0 1.0.0.0/32 is subnetted, 1 subnets D 1.1.1.1 [90/435200] via 192.168.23.2, 00:00:42, Ethernet0/0 C 192.168.23.0/24 is directly connected, Ethernet0/0 D* 0.0.0.0/0 [90/307200] via 192.168.23.2, 00:00:42, Ethernet0/0
确认R2或者R3可以正常访问1.1.1.1。
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R3#ping 1.1.1.1 Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 1.1.1.1, timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5), round-trip min/avg/max = 52/72/100 ms
R3#sh ip route Gateway of last resort is 192.168.23.2 to network 0.0.0.0 D 192.168.12.0/24 [90/307200] via 192.168.23.2, 00:13:04, Ethernet0/0 C 192.168.23.0/24 is directly connected, Ethernet0/0 D*EX 0.0.0.0/0 [170/2636800] via 192.168.23.2, 00:01:34, Ethernet0/0
R3#ping 1.1.1.1 Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 1.1.1.1, timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5), round-trip min/avg/max = 64/79/116 ms
R3#sh ip route Gateway of last resort is 192.168.23.2 to network 0.0.0.0 D 192.168.12.0/24 [90/307200] via 192.168.23.2, 00:20:00, Ethernet0/0 C 192.168.23.0/24 is directly connected, Ethernet0/0 D* 0.0.0.0/0 [90/332800] via 192.168.23.2, 00:00:29, Ethernet0/0
我们发现缺省成功的产生了,而且是来自于内部的D*条目。下面查看R3能否访问1.1.1.1
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R3#ping 1.1.1.1 Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 1.1.1.1, timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5), round-trip min/avg/max = 56/71/100 ms
R1#sh ip route Gateway of last resort is not set C 192.168.12.0/24 is directly connected, Ethernet0/0 1.0.0.0/32 is subnetted, 1 subnets C 1.1.1.1 is directly connected, Loopback0 S 10.0.0.0/8 is directly connected, Null0 D 192.168.23.0/24 [90/307200] via 192.168.12.2, 00:24:54, Ethernet0/0
R1#sh ip route Gateway of last resort is not set C 192.168.12.0/24 is directly connected, Ethernet0/0 1.0.0.0/32 is subnetted, 1 subnets C 1.1.1.1 is directly connected, Loopback0 S* 10.0.0.0/8 is directly connected, Null0 D 192.168.23.0/24 [90/307200] via 192.168.12.2, 00:27:14, Ethernet0/0
R3#sh ip route Gateway of last resort is 192.168.23.2 to network 10.0.0.0 D 192.168.12.0/24 [90/307200] via 192.168.23.2, 00:29:06, Ethernet0/0 D* 10.0.0.0/8 [90/307200] via 192.168.23.2, 00:00:08, Ethernet0/0 C 192.168.23.0/24 is directly connected, Ethernet0/0
R3#ping 1.1.1.1 Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 1.1.1.1, timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5), round-trip min/avg/max = 60/72/100 ms