How to open a port for eth1 ?

Senthilv · 02-04-2011, 01:34 AM

I have Linux server (centos) in my company ,
In Server have two Ethernet card we are using one for getting internet connection via eth0 and another one is passing network is shared through this ethernet eth1

Network is shared through this linux squid proxy server to Windows client .

But thing is ....

In Windows client Browsing internet via proxy is fine . But while ping google.com in cmd it say could not connect

How to rectify this ...Tell me any one ...

Noway2 · 02-04-2011, 05:59 AM

You should be able to use iptables' NAT functionality to pass the ICMP traffic from one interface to the other.

For example see the following code. It will probably take some tweaking for your purposes (I don't claim that as it is written it will work as you intend) but should give you the idea.

Code:

To accept PING:
-A INPUT -p icmp -m icmp --icmp-type echo-request -j ACCEPT
-A INPUT -m state --state RELATED,ESTABLISHED -j ACCEPT
To pass between the interfaces:
iptables -t nat -A POSTROUTING -i eth0 -o eth1 -j MASQUERADE

DrOzz · 02-04-2011, 07:55 AM

Let's see your firewall script that you are presently using. I use this same network setup in 60 schools and don't have an issue with outgoing pings from Windows clients on the network. But with what Noway2 has shown, if you do have to specify some rules to allow, I'd say you'd have to use OUTPUT rules as opposed to INPUT because INPUT would be defining ICMP coming from the outside to eth0.

That is if I am understanding correctly that you want to ping out from a windows client going through eth1, then out through eth0 to your destination ping?