Can work Cent OS as Nat router

[nikhil]

Hi ,

I am Ben, I need to configure centos 6 as Nat router.
I mean to say I have six private ip ad 6 public ip now i need to configure cent os 6 as NAT router.


Please tell me any one how can i do this one task.

Thanks,
Ben

[eugene.ievlev]

Hi,

First of all - check net.ipv4.ip_forward setting in /etc/sysctl.conf
For configuration of routing you can use command - route, for checking - netstat.
Configuration files which can help you:
/etc/sysconfig/network-scripts/ifcfg-eth{your interface} This file contains your network card settings
/etc/sysconfig/network This file contains various other settings, mainly the hostname and gateway
/etc/resolv.conf This file contains our search domain and nameservers
/etc/hosts Hostname and other entries for local machines not in DNS

Next big step - configuration iptables for configuration of NAT (like default solution).

Read mans, and good luck!

[vonskippy]

viewtopic.php?f=13&t=45949

[nikhil]

Dear eugene,


Thanks and very much for helpful support.
i have configure cent os as per you information now
I have one hp hardware and there is two nick card and,
I have configure two nick card eth0 for ISP and eth1 for lan interface and i have configure as below please check.

modprobe iptable_nat
echo 1 > /proc/sys/net/ipv4/ip_forward
iptables --flush
iptables -A FORWARD -i eth0 -j ACCEPT
iptables -A FORWARD -o eth0 -j ACCEPT
iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE
iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE
iptables -A PREROUTING -t nat -d 18.22.26.22 -i eth0 -j DNAT --to-destination 192.168.1.64
iptables -t nat -A POSTROUTING -o eth0 -s 192.168.1.64 -j SNAT --to 18.22.26.22
iptables -t nat -L -n -v


Thanks,
Ben

[gerald_clark]

Just buy a router.
Your chances of building a secure router are slim.

[nikhil]

Dear Sir,

I have one router but steel i need to configure centos as well as.

Can i do this imp task.

Thanks,
Ben

[eugene.ievlev]

modprobe iptable_nat
echo 1 > /proc/sys/net/ipv4/ip_forward
iptables --flush
iptables -A FORWARD -i eth0 -j ACCEPT
iptables -A FORWARD -o eth0 -j ACCEPT
iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE
iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE
iptables -A PREROUTING -t nat -d 18.22.26.22 -i eth0 -j DNAT --to-destination 192.168.1.64
iptables -t nat -A POSTROUTING -o eth0 -s 192.168.1.64 -j SNAT --to 18.22.26.22
iptables -t nat -L -n -v

Hi Ben,
Seems good. But configuration of firewall is individual for each case. And i don't recommend open all ports

Good luck,
Eugene