Links on Subdomain broken after htaccess rewrite - .htaccess

Question

Problems:
1) Need ALL urls to always redirect to non-www
2) domain.com needs to automatically redirect to sub.domain.com
Based on other articles here, I've tried:
Options +FollowSymLinks -MultiViews
RewriteEngine on
RewriteBase /
RewriteCond %{HTTP_HOST} ^www\.(sub\.domain\.com)$ [NC]
RewriteRule ^ http:://%1%{REQUEST_URI} [R=301,L]
[had to insert an extra ":" for this to post]
Which "works", but then all of the links on my site 404.
Can you point out what I'm doing wrong?

Answer 1

Try this code :
RewriteEngine on
RewriteCond %{HTTP_HOST} ^www\.(.*)$
RewriteRule ^(.*)$ http://%1/$1 [R=301,L]
RewriteCond %{HTTP_HOST} ^domain\.com$
RewriteRule ^(.*)$ http://sub.domain.com/$1 [R=301,L]

Answer 2

In the comment you provided on Jul. 26th, the rule
RewriteRule ^(.*)\.html$ $1.php [nc]
is used to rewrite all requests for html files to requests for php files. This is typically done for SEO, to make the pages appear as static html instead of dynamic php in situations where php is primarily used to reduce code duplication.
In these cases, it is typical that all the page files on the server exist only in php format, and not html format. Therefore, without this rule, all links to .html files will remain as requests to the server for .html files, which will result in many 404s.
I would suggest you simply insert this rule in your .htaccess block in the original question, at the end of your statements. They ought to play well together. The result for completeness:
Options +FollowSymLinks -MultiViews
RewriteEngine on
RewriteBase /
RewriteCond %{HTTP_HOST} ^www\.(sub\.domain\.com)$
RewriteRule ^http://%1%{REQUEST_URI} [R=301]
RewriteRule ^(.*)\.html$ $1.php [NC]
*My mistake, the flags [NC] and [OR] are definitely valid for RewriteCond statements.