CentOS 7 下配置ip forward(虚拟路由器)

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,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,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,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 1000@H_722_26@ms
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,time 1000@H_722_26@ms
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,time 1002@H_722_26@ms
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=1@H_722_26@ms TTL=63
Reply from 172.24.8.131: bytes=32 time=1@H_722_26@ms TTL=63

注，如果测试有问题，请考虑是否被防火墙拦住。