what is cpanel

Every once in a while a hosting provider has to change an IP address for a single user or even an entire server on the fly. If you’ll try do this the usual way, by changing the IP address in WHM you can expect downtime ranging from several minutes to several hours until the DNS cache is cleared.

While cPanel does not officially allow accounts to have more than one IP address, there is no such restriction for Apache. So the solution is to override the default cPanel configurations with your own.

In the first example I will show you how to do this with a single site and in the second one I will focus on the entire server.

  1. Change a single site to work from multiple IP addresses:

In this example we want to alter the domain example.com which runs on the IP
address: 185.20.1.1 to also run on the IP address: 185.20.2.2 – assuming that both IP addresses are already configured on the server.

Apache’s configuration file is automatically generated at on of the following locations.

On EASY APACHE 4 based servers:

# /etc/apache2/conf/httpd.conf

On EASY APACHE 3 based servers:

# /usr/local/apache/conf/httpd.conf

And a large capital letters warning us:

DO NOT EDIT. AUTOMATICALLY GENERATED. USE INCLUDE FILES IF YOU NEED TO MAKE A CHANGE

While there is no use editing the file, we can pull all the VHOST info from it.

It will look like this:

<VirtualHost 185.20.1.1:80 >
 ServerName example.com
 ServerAlias mail.example.com www.example.com
 DocumentRoot /home/example/public_html
 ServerAdmin webmaster@example.com
 UseCanonicalName Off

... more settings here ...

</VirtualHost>

If you are using an SSL certificate there is another block for the SSL virutal host:

<VirtualHost 185.20.1.1:443 >
 ServerName example.com
 ServerAlias mail.example.com www.example.com
 DocumentRoot /home/example/public_html
 ServerAdmin webmaster@example.com
 UseCanonicalName Off

... more settings here ...

</VirtualHost>

We need to copy both of these blocks to the file:

/usr/local/apache/conf/includes/pre_virtualhost_global.conf

for EasyApache3

OR

/etc/apache2/conf.d/includes/pre_virtualhost_global.conf

for EasyApache4

Afterwards edit the opening line on each VHOST block so it includes both of the first and the second IP addresses like:

<VirtualHost 185.20.1.1:80 185.20.2.2:80>

...vhost settings...

</VirtualHost>

<VirtualHost 185.20.1.1:443 185.20.2.2:443>

...vhost settings...

</VirtualHost>

Save and run:

/scripts/rebuildhttpdconf

make sure you get no errors and then restart Apache:

/scripts/restartsrv_httpd

That’s it, you’re good to go 

2. Change a server to load from multiple IP addresses:

Instead of copying an entire VHOST, as in the previous example, we will edit the default template that cPanel uses to build VirtualHosts.

Step 1:
 cd /var/cpanel/templates/apache2_4/

Step 2:

cp vhost.default vhost.local
cp ssl_vhost.default ssl_vhost.local

Step 3: Edit each file:

In the vhost.local file change the first line from:

<VirtualHost[% FOREACH ipblock IN vhost.ips %] [% ipblock.ip %]:[% ipblock.port %][% END %]>

To:

<VirtualHost 185.20.1.1:80 185.20.2.2:80 >

In ssl_vhost.local file change the first line from:

<VirtualHost[% FOREACH ipblock IN vhost.ips %] [% ipblock.ip %]:[% ipblock.port %][% END %]>

To:

<VirtualHost 185.20.1.1:443 185.20.2.2:443 >

Step 4:

/scripts/rebuildhttpdconf
/scripts/restartsrv_httpd

By completing all the above steps, all of the accounts on the server will run from both IPs addresses.

If you have accounts that uses a private IP address, you can use a combination of both methods. Change the template to run from the two main addresses as in method 2 and then copy the the virtual host settings as in method 1, but remember to change the IP address to the site’s private IP address.