Linux 中ip forward功能是一个比较方便实用的功能，只需要简单配置，添加几条路由，即可实现ip转发。本文基于CentOS 7下采取一台机器充当虚拟路由，来实现Windows环境与Linux环境中相互通信。具体见下文，供大家参考。
一、环境及需求说明
本地测试环境，由于Win7+VMware这台机器网卡太新，无法被VMware EXSi识别，无奈之下就直接装了个Win7，然后再上面基于Vmware workstation 12开启了一些临时测试的虚拟机。其次本地直连网段192.168.1.0 IP有限，而又希望直接从本机(如图Win10) ssh连接到这些虚拟机，因此考虑使用Linux的ip转发功能来实现。
上述图片中已经列出了各个节点的IP信息，红色的虚拟机充当软路由，配置好之后，实现Win10 直接ssh到虚拟机。
二、虚拟路由服务器配置
###查看网卡信息 [root@centos7-router ~]# ip addr 1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00 inet 127.0.0.1/8 scope host lo valid_lft forever preferred_lft forever inet6 ::1/128 scope host valid_lft forever preferred_lft forever 2: eno16777728: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000 link/ether 00:0c:29:9c:eb:2d brd ff:ff:ff:ff:ff:ff inet 172.24.8.254/24 brd 172.24.8.255 scope global eno16777728 valid_lft forever preferred_lft forever inet6 fe80::20c:29ff:fe9c:eb2d/64 scope link valid_lft forever preferred_lft forever 3: eno33554960: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000 link/ether 00:0c:29:9c:eb:37 brd ff:ff:ff:ff:ff:ff inet 192.168.1.175/24 brd 192.168.1.255 scope global dynamic eno33554960 valid_lft 82384sec preferred_lft 82384sec inet6 fe80::20c:29ff:fe9c:eb37/64 scope link valid_lft forever preferred_lft forever ###查看路由表 [root@centos7-router ~]# route -n Kernel IP routing table ###缺省情况下，每块网卡都有一个基于本网段的路由记录 Destination Gateway Genmask Flags Metric Ref Use Iface 0.0.0.0 192.168.1.1 0.0.0.0 UG 100 0 0 eno33554960 172.24.8.0 0.0.0.0 255.255.255.0 U 100 0 0 eno16777728 192.168.1.0 0.0.0.0 255.255.255.0 U 100 0 0 eno33554960 ###使用ip命令方式查看路由 [root@centos7-router ~]# ip route list default via 192.168.1.1 dev eno33554960 proto static metric 100 172.24.8.0/24 dev eno16777728 proto kernel scope link src 172.24.8.254 metric 100 192.168.1.0/24 dev eno33554960 proto kernel scope link src 192.168.1.175 metric 100 ###开启ip forward [root@centos7-router ~]# cp /usr/lib/sysctl.d/50-default.conf /usr/lib/sysctl.d/50-default.conf.bk [root@centos7-router ~]# echo "net.ipv4.ip_forward = 1" >>/usr/lib/sysctl.d/50-default.conf [root@centos7-router ~]# grep ip_forward /usr/lib/sysctl.d/50-default.conf net.ipv4.ip_forward = 1 [root@centos7-router ~]# sysctl -p ###如不生效重启一下OS
三、CentOS7-a主机下添加路由
###查看当前主机ip 信息 [root@centos7-a ~]# ip addr list 1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00 inet 127.0.0.1/8 scope host lo valid_lft forever preferred_lft forever inet6 ::1/128 scope host valid_lft forever preferred_lft forever 2: eno16777728: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000 link/ether 00:0c:29:57:26:9d brd ff:ff:ff:ff:ff:ff inet 172.24.8.131/24 brd 172.24.8.255 scope global dynamic eno16777728 valid_lft 1088sec preferred_lft 1088sec inet6 fe80::20c:29ff:fe57:269d/64 scope link valid_lft forever preferred_lft forever ###查看当前主机路由信息 [root@centos7-a ~]# ip route list 172.24.8.0/24 dev eno16777728 proto kernel scope link src 172.24.8.131 metric 100 [root@centos7-a ~]# # Author : Leshami [root@centos7-a ~]# # Blog : http://blog.csdn.net/leshami [root@centos7-a ~]# ip route add default via 172.24.8.254 [root@centos7-a ~]# ip route list default via 172.24.8.254 dev eno16777728 172.24.8.0/24 dev eno16777728 proto kernel scope link src 172.24.8.131 metric 100 ###测试到虚拟路由器网关ip连通性 [root@centos7-a ~]# ping 172.24.8.254 -c 2 PING 172.24.8.254 (172.24.8.254) 56(84) bytes of data. 64 bytes from 172.24.8.254: icmp_seq=1 ttl=64 time=0.268 ms 64 bytes from 172.24.8.254: icmp_seq=2 ttl=64 time=0.302 ms --- 172.24.8.254 ping statistics --- 2 packets transmitted, 2 received, 0% packet loss, time 1000ms rtt min/avg/max/mdev = 0.268/0.285/0.302/0.017 ms ###测试到虚拟路由器ip连通性 [root@centos7-a ~]# ping 192.168.1.175 -c 2 PING 192.168.1.175 (192.168.1.175) 56(84) bytes of data. 64 bytes from 192.168.1.175: icmp_seq=1 ttl=64 time=0.475 ms 64 bytes from 192.168.1.175: icmp_seq=2 ttl=64 time=0.443 ms --- 192.168.1.175 ping statistics --- 2 packets transmitted, 2 received, 0% packet loss, time 1000ms rtt min/avg/max/mdev = 0.443/0.459/0.475/0.016 ms
四、Windows 10下配置路由
###当前环境
C:>systeminfo | findstr Build
OS Version: 10.0.14393 N/A Build 14393
OS Build Type: Multiprocessor Free
###查看当前的路由信息
C:>route print -4
===========================================================================
Interface List
7...54 ab 3a xx b8 ea ......Intel(R) Ethernet Connection I219-V
21...ac 2b 6e 5f 3b 57 ......Microsoft Wi-Fi Direct Virtual Adapter
......
===========================================================================
IPv4 Route Table
===========================================================================
Active Routes:
Network Destination Netmask Gateway Interface Metric
0.0.0.0 0.0.0.0 192.168.1.1 192.168.1.242 35
127.0.0.0 255.0.0.0 On-link 127.0.0.1 331
127.0.0.1 255.255.255.255 On-link 127.0.0.1 331
127.255.255.255 255.255.255.255 On-link 127.0.0.1 331
172.24.10.0 255.255.255.0 On-link 172.24.10.1 291
172.24.10.1 255.255.255.255 On-link 172.24.10.1 291
172.24.10.255 255.255.255.255 On-link 172.24.10.1 291
192.168.1.0 255.255.255.0 On-link 192.168.1.242 291
192.168.1.242 255.255.255.255 On-link 192.168.1.242 291
192.168.1.255 255.255.255.255 On-link 192.168.1.242 291
192.168.16.0 255.255.255.0 On-link 192.168.16.1 291
192.168.16.1 255.255.255.255 On-link 192.168.16.1 291
192.168.16.255 255.255.255.255 On-link 192.168.16.1 291
224.0.0.0 240.0.0.0 On-link 127.0.0.1 331
224.0.0.0 240.0.0.0 On-link 192.168.1.242 291
224.0.0.0 240.0.0.0 On-link 192.168.16.1 291
224.0.0.0 240.0.0.0 On-link 172.24.10.1 291
255.255.255.255 255.255.255.255 On-link 127.0.0.1 331
255.255.255.255 255.255.255.255 On-link 192.168.1.242 291
255.255.255.255 255.255.255.255 On-link 192.168.16.1 291
255.255.255.255 255.255.255.255 On-link 172.24.10.1 291
===========================================================================
Persistent Routes:
None
###添加持久化路由
C:>route add 172.24.8.0 mask 255.255.255.0 192.168.1.175 -p
OK!
C:>route print -4
IPv4 Route Table
===========================================================================
Active Routes:
Network Destination Netmask Gateway Interface Metric
0.0.0.0 0.0.0.0 192.168.1.1 192.168.1.242 35
127.0.0.0 255.0.0.0 On-link 127.0.0.1 331
127.0.0.1 255.255.255.255 On-link 127.0.0.1 331
127.255.255.255 255.255.255.255 On-link 127.0.0.1 331
172.24.8.0 255.255.255.0 192.168.1.175 192.168.1.242 36
172.24.10.0 255.255.255.0 On-link 172.24.10.1 291
172.24.10.1 255.255.255.255 On-link 172.24.10.1 291
172.24.10.255 255.255.255.255 On-link 172.24.10.1 291
192.168.1.0 255.255.255.0 On-link 192.168.1.242 291
192.168.1.242 255.255.255.255 On-link 192.168.1.242 291
192.168.1.255 255.255.255.255 On-link 192.168.1.242 291
192.168.16.0 255.255.255.0 On-link 192.168.16.1 291
192.168.16.1 255.255.255.255 On-link 192.168.16.1 291
192.168.16.255 255.255.255.255 On-link 192.168.16.1 291
224.0.0.0 240.0.0.0 On-link 127.0.0.1 331
224.0.0.0 240.0.0.0 On-link 192.168.1.242 291
224.0.0.0 240.0.0.0 On-link 192.168.16.1 291
224.0.0.0 240.0.0.0 On-link 172.24.10.1 291
255.255.255.255 255.255.255.255 On-link 127.0.0.1 331
255.255.255.255 255.255.255.255 On-link 192.168.1.242 291
255.255.255.255 255.255.255.255 On-link 192.168.16.1 291
255.255.255.255 255.255.255.255 On-link 172.24.10.1 291
===========================================================================
Persistent Routes: ###以下为添加的持久化路由记录
Network Address Netmask Gateway Address Metric
172.24.8.0 255.255.255.0 192.168.1.175 1
===========================================================================
五、验证两边连通性
###从Linux端ping windows 10 [root@centos7-a ~]# ping 192.168.1.242 -c 2 PING 192.168.1.242 (192.168.1.242) 56(84) bytes of data. 64 bytes from 192.168.1.242: icmp_seq=1 ttl=63 time=1.70 ms 64 bytes from 192.168.1.242: icmp_seq=2 ttl=63 time=1.10 ms --- 192.168.1.242 ping statistics --- 2 packets transmitted, 2 received, 0% packet loss, time 1002ms rtt min/avg/max/mdev = 1.101/1.404/1.707/0.303 ms ###从windows 10端ping Linux C:>ping 172.24.8.131 -t Pinging 172.24.8.131 with 32 bytes of data: Reply from 172.24.8.131: bytes=32 time=1ms TTL=63 Reply from 172.24.8.131: bytes=32 time=1ms TTL=63
注，如果测试有问题，请考虑是否被防火墙拦住。
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