CentOS7下配置ip forward的方法

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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 addr1: lo:  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 forever2: eno16777728:  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 forever3: eno33554960:  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 -nKernel 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 Iface0.0.0.0    192.168.1.1  0.0.0.0    UG  100  0    0 eno33554960172.24.8.0   0.0.0.0    255.255.255.0 U  100  0    0 eno16777728192.168.1.0  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 listdefault 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.confnet.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 list1: lo:  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 forever2: eno16777728:  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 list172.24.8.0/24 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 listdefault 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 ms64 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 1000msrtt 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 2PING 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 ms64 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 1000msrtt 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 BuildOS Version:        10.0.14393 N/A Build 14393OS 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-V21...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 -pOK!C:\>route print -4IPv4 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 ms64 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 1002msrtt min/avg/max/mdev = 1.101/1.404/1.707/0.303 ms###从windows 10端ping LinuxC:\>ping 172.24.8.131 -tPinging 172.24.8.131 with 32 bytes of data:Reply from 172.24.8.131: bytes=32 time=1ms TTL=63Reply 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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