If the rule is used in a .htaccess file, use
RewriteCond %{REQUEST_URI} !^/000_ROUTE.php$
RewriteRule . /000_ROUTE.php [L]
If it's in your VirtualHost-block or main config file instead, use
RewriteCond %{REQUEST_URI} !^/000_ROUTE.php$
RewriteRule /. /000_ROUTE.php [L]
(the only difference is the leading slash on the RewriteRule).
The first thing Apache httpd does before evaluating the RewriteConds is to evaluate the RewriteRule. Putting the condition into the Rule (and in this case the condition is that there is at least one character after the slash) saves Apache having to evaluate the RewriteCond entirely for requests at "/". The RewriteCond ensures that you don't end up in a loop of rewrites -- after all, 000_ROUTE.php is not "/", either.)
Depending on how often that rule will get hit (i.e. if you expect it to get hit a lot and thus separating out a RewriteCond is just going to add overhead), you could also condense it into
RewriteRule ^(?!000_ROUTE.php). /000_ROUTE.php [R,L]
for .htaccess or -contexts
RewriteRule ^/(?!000_ROUTE.php). /000_ROUTE.php [R,L]
for or server-contexts.