Subdomain redirection to external subdomain

Question

I need to create a redirection from my own subdomain to an external subdomain, like subdomain.domain.com -> subdomain.external.com. So if anyone try to enter in my subdomain, it redirects automatically to subdomain.external.com.

Thanks all.

EDIT:

I tried via DNS in cPanel/WHM with CNAME and in .htaccess with:

<IfModule mod_rewrite.c>
RewriteEngine On
SetEnv HTTP_MOD_REWRITE On
RewriteBase /
RewriteRule ^index\.php$ - [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php [L]
RewriteCond %{HTTP_HOST} ^subdomain\.domain\.com$  [NC]
RewriteRule ^(.*)$ https://subdomain.external.com/$1 [R=301,NC,L,QSA]
</IfModule>

But nothing works :/

Answer 1

The rules are applied in order, so it would not find a corresponding file and send you to /index.php

<IfModule mod_rewrite.c>
RewriteEngine On
SetEnv HTTP_MOD_REWRITE On
RewriteBase /

# First test for the redirect
RewriteCond %{HTTP_HOST} ^subdomain\.domain\.com$ [NC]
RewriteRule ^(.*)$ https://subdomain.external.com/$1 [R=301,NC,L,QSA]

RewriteRule ^index\.php$ - [L]

RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php [L]

</IfModule>

The [L], which you can rewrite [last], means that rewrite rules coming after that line are ignored.