R1 :
conf t
int f0/0
no shutdown
ip add 192.168.1.1 255.255.255.0
no ip routing
end
R2 f0/0:
conf t
int f0/0
no shutdown
ip add 192.168.1.254 255.255.255.0
end
R2 f1/0:
conf t
int f0/0
no shutdown
ip add 192.168.2.254 255.255.255.0
end
R3 :
conf t
int f0/0
no shutdown
ip add 192.168.2.1 255.255.255.0
no ip routing
end
在R1里面添加 ip route 0.0.0.0 0.0.0.0 192.168.1.254映射从R1的路由表,然后ping 192.168.2.1 。思科linux 下是5个包出去，5个包返回。windows下是4个
分析协议可以看到TTL(Time to live)值减1.