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the networking features in Linux are really amazing , in this post I want to show you how you can setup a general IP proxy on a specific port.
in order to write the required script open a new file named proxy :

1 nano proxy

copy and paste the following script into the file :

1 YourIP=X.X.X.X
2 TargetIP=Y.Y.Y.Y
3 Port=Z
4
5 iptables -t nat -A PREROUTING -p tcp –dport $Port -d $YourIP -j DNAT –to $TargetIP
6 iptables -t nat -A POSTROUTING -p tcp –dport $Port -d $TargetIP -j SNAT –to $YourIP

Change X.X.X.X to your nic IP.
Change Y.Y.Y.Y to target IP.
and Change Z to the port which needs to be proxied.
save and close the file.
make it executable and run it :

1 chmod +x proxy
2 ./proxy

enable IPv4 forwarding in sysctl.conf :

1 nano /etc/sysctl.conf

and make sure you have the following line uncommented :

1 net.ipv4.ip_forward=1

and apply the changes :

1 sysctl -p

one of the problems I had on one of my cPanel servers was that some people were using download managers to download files from server , so hundreds of connections were being ESTABLISHED to Apache and it was becoming like a dos attack and causing Apache to become non responsive.
so here is what I did to limit connections per IP in a cPanel hosting server :
there is an Apache module named mod_limitipconn which will take care of it for us.
first download the latest version of mod_limitipconn from this site : http://dominia.org/djao/limitipconn2.html
decompress and install it.
at current time the latest version is 0.23.
view source
print?
1 wget http://dominia.org/djao/limit/mod_limitipconn-0.23.tar.bz2
2 tar jxvf mod_limitipconn-0.23.tar.bz2
3 cd mod_limitipconn-0.23
4 usr/local/apache/bin/apxs -cia mod_limitipconn.c

next step is to add the required configuration to the Apache config file , we can add this directly to the end of httpd.conf file but the problem is that if we do this , the httpd.conf will be overwritten by easyapache so we will use include files to add our config.
login into your WHM panel , and follow the following menu items :
Main >> Service Configuration >> Apache Configuration >> Include Editor
on the Post VirtualHost Include section , choose All Versions from drop down menu and add the following config into it :
view source
print?
1
2
3 MaxConnPerIP 10
4 NoIPLimit images/*
5
6

then click on update and restart Apache server.

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