apache 2.2 - apache2 configuration for blog.example.com not working

I have my blog running at a server with ip 10.10.10.10(not real).

There is only one virtual host for this blog on the server.

Here is the apache configuration:

VirtualHost star:80
ServerName blog.example.com
ServerAlias blog.example.com
ServerAdmin ab@example.com
DocumentRoot /var/www/
RewriteEngine on
RewriteCond %{HTTP_HOST} ^[^.]+.example.com$
RewriteRule ^(.+) %{HTTP_HOST}$1 [C]
RewriteRule ^([^.]+).example.com/(.*) /var/www/$1
DirectoryIndex index.php

Directory /var/www/
AllowOverride All
Order Deny,Allow
Allow from all
/Directory
/VirtualHost

My DNS blog.example.com is pointing to this ip address 10.10.10.10 .

When I load first time blog.example.com it loads correct with no problems. But whenever i click a link it shows url like http://10.10.10.10/login.php etc.

I am a newbie. Please help me set up this.
Is there any problem with the rewrite rule ?