Linux hosts implement simple routing and forwarding functions

as long as the a Few simple routing entries are added to the Linux host, which can act as a simple router.

in the actual production of the bad environment, when we need a router as simple as forwarding data, but without a router on hand, we can designate a single The Linux host acts as a simple router, enabling simple forwarding of routes.

the above-mentioned complaints are especially simple, so just to implement the simple routing function, if you want to implement a very complex function, a single Linux hosts may not be able to implement the conditions you want.

experiment bad ": vmware 4 virtual host, host name r1 r2 two hosts ( all system ) acting as a router, and hostname centos7.2 (1) and centos7.2 (2) two hosts as test hosts.

here is an experimental topology diagram :

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Here are the experimental steps:

1>. The firewall affects the routing forwarding feature, first emptying R1 and the R2 firewall rules on two hosts.

[Email protected] ~]# iptables-f[[email protected] ~]# iptables-f

2> Linux System, the default route forwarding function is closed, we need to modify the configuration file to open the route forwarding function.

routing forwarded configuration file /proc/sys/net/ipv4/ip_forward

View and set The /proc/sys/net/ipv4/ip_forward on the R1

[[email protected] ~]# Cat/proc/sys/net/ipv4/ip_forward0[[email protected] ~]# echo "1" >/proc/sys/net/ipv4/ip_ Forward[[email protected] ~]# cat/proc/sys/net/ipv4/ip_forward1

View and set The /proc/sys/net/ipv4/ip_forward on the R2

[[email protected] ~]# Cat/proc/sys/net/ipv4/ip_forward0[[email protected] ~]# echo "1" >/proc/sys/net/ipv4/ip_ Forward[[email protected] ~]# cat/proc/sys/net/ipv4/ip_forward1

3>. gave R1 Host eth0 and the eth1 Interface Configuration IP Address

[email protected] network-scripts]# cat ifcfg-eth0device=eth0hwaddr=00:0c:29:b3:32:cctype=ethernetuuid= A7f94e4f-1f87-439f-a044-9888cc8ddc7conboot=yesnm_controlled=nobootproto=noneipaddr=10.0.0.2prefix=8[[email Protected] network-scripts]# Cat ifcfg-eth1device=eth1type=ethernetonboot=yesnm_controlled=nonebootproto= Staticipaddr=172.16.0.1prefix=16

4>. gave R2 Host eth1 and the eth2 Interface Configuration IP Address

[email protected] network-scripts]# cat ifcfg-eth1device=eth1type=ethernetonboot=yesnm_controlled=yesbootproto= Staticipaddr=172.16.0.2prefix=16[[email protected] network-scripts]# cat ifcfg-eth2device=eth2bootproto=noneipaddr =192.168.1.1netmask=255.255.255.0

5>. temporarily designate a host Centos7.2 (1) and the Centos7.2 (2) IP address.

Temporary designation Centos7.2 (1) eno16777736 IP address :

[Email protected] sysconfig]# ifconfig eno16777736 10.0.0.1

Temporary designation Centos7.2 (2) eno16777736 IP address :

[Email protected] ~]# ifconfig eno16777736 192.168.1.2

6>. The IP address is already configured, now to add some routing rules on the router, you need to add the gateway configuration to the test host.

a>. in add A route entry to the 192.168.1.0 network segment on the R1 host

[Email protected] network-scripts]# Route add-net 192.168.1.0/24 GW 172.16.0.2 Dev eth1

View Host route entry for R1 :

[Email protected] network-scripts]# IP route192.168.96.0/24 dev eth2 proto kernel scope link src 192.168.96.137 metri C 1 192.168.1.0/24 via 172.16.0.2 dev eth1 172.16.0.0/16 dev eth1 proto kernel scope link src 172.16.0.1 metric 1 169. 254.0.0/16 Dev eth0 scope link metric 1002 10.0.0.0/8 dev eth0 proto kernel scope link src 10.0.0.2

b>. in add A route entry to the 192.168.1.0 network segment on the R2 host

[Email protected] network-scripts]# Route add-net 10.0.0.0/8 GW 172.16.0.1 Dev eth1

View Host route entry for R2 :

[Email protected] network-scripts]# IP route192.168.96.0/24 dev eth3 proto kernel scope link src 192.168.96.139 metri C 1 192.168.1.0/24 Dev eth2 proto kernel scope link src 192.168.1.1 metric 1 172.16.0.0/16 dev eth1 Proto kernel SCO PE link SRC 172.16.0.2 metric 1 10.0.0.0/8 via 172.16.0.1 Dev eth1

C> To test two hosts centos7.2 (1) and centos7.2 (2) Add the specified gateway

[[email protected] sysconfig]# route add-net default GW 10.0.0.2[[email protected] ~]# route add-net default GW 192.168. 1.1

7>. Test :

use centos7.2 (1) to Ping the host of centos7.2 (2) :

[Email protected] sysconfig]# ping 192.168.1.2PING 192.168.1.2 (192.168.1.2) (+) bytes of data.64 bytes from 192.168.1 .2:icmp_seq=1 ttl=62 time=16.2 ms64 bytes from 192.168.1.2:icmp_seq=2 ttl=62 time=1.02 ms64 bytes from 192.168.1.2:icmp _seq=3 ttl=62 time=1.39 ms64 bytes from 192.168.1.2:icmp_seq=4 ttl=62 time=1.06 ms ....

It is clear that two hosts are connected to one another.

Linux hosts implement simple routing and forwarding functions