Centos6.5 for routing, NAT, and DHCP

Centos6.5 for routing, NAT, and DHCP

Lab environment:

Route (dual Nic Linux host ):

Eth0 (Internet Nic ):

IPADDR = 10.100.56.46

NETMASK = 255.255.255.0

GATEWAY = 10.100.56.1

Eth1 (intranet Nic ):

IPADDR = 174.36.10.1

NETMASK = 255.255.255.0

Client (single Nic Linux host ):

Eth0:

IPADDR = 174.36.10.2

NETMASK = 255.255.255.0

GATEWAY = 174.36.10.1

Vi/etc/sysconfig/network // configure the Gateway

Step 1:

Edit the sysctl. conf file to enable IP forwarding.

Vi/etc/sysctl. conf

Change net. ipv4.ip _ forward = 0 to net. ipv4.ip _ forward = 1.

Type sysctl-p // to make the configuration take effect immediately

Step 2:
Modify the iptables File
Iptables-F
Iptables-t nat-a postrouting-o eth0-j MASQUERADE
Iptables-t filter-a forward-I eth0-o eth1-j ACCEPT
Iptables-t filter-a forward-I eth1-o eth0-j ACCEPT
Type service iptables save // save iptables configuration

After completing the routing and nat settings, cilent can ping the internet.

Step 3: Configure DHCP

Yum-y install dhcp // install DHCP Service

Cp/etc/dhcp/dhcpd. conf/etc/dhcp/dhcpd. conf. bak // back up the dhcpd. conf file

Vi/etc/dhcp/dhcpd. conf // edit the configuration file

Subnet 174.36.10.0 netmask 255.255.255.0 {
Range 174.36.10.20 174.36.10.250;
Option domain-name-servers 114.114.114.114;
Option routers 174.36.10.1;
Option broadcast-address 174.36.10.255;
Default-lease-time 600;
Max-lease-time 7200;
}

Service dhcpd start // start the service

Chkconfig dhcpd on // set to boot

Vi/etc/sysconfig/dhcp // specify the network interface of the DHCP service

DHCPDARGS = eth1

Comment out the static IP configuration of the client, and change BOOTPROTO to dhcp.

Service network restart // restart the network service

View the IP address (obtained IP: 174.36.10.20)

Pingwww.baidu.com