srv1: eth0: 172.16.254.101 DGW: 172.16.254.102srv2: eth0: 172.16.254.102 eth1: 192.168.254.102srv3: eth0: 192.168.254.103 DGW: 192.168.254.102
由srv2来负责路由转发
打开包转发srv2#echo 1 > /proc/sys/net/ipv4/ip_forward