Practical Migration Strategy for IPv6 Web Services

If we have web servers that only support IPv4, a simple solution is to configure a web server with IPv6 support and use a Reverse Proxy. One IPv6 friendly solution for that is to use Apache HTTP Server with modules for proxying.

Configure it

Setting up a reverse proxy for an entire website is fairly straightforward. As an example I present the case study from my institution where we have some web servers that do not support IPv4 and for this we set up a server with IPv6 support and the reverse proxy with Apache. The configuration that I show is only for a site, but for others is the same. In my IPv6 Web Server I use Debian, Apache2.2 with modules for proxying.

<VirtualHost [IPv6_address_of_server]:80>
ServerName www.foo.institution.org
ServerAlias foo.institution.org

ProxyPass / http://www.ipv4foo.institution.org/
ProxyPassReverse / http://www.ipv4foo.institution.org/
ProxyPreserveHost On

LogLevel warn
ErrorLog /var/log/apache2/foo-error.log
CustomLog /var/log/apache2/foo-access.log combined

</VirtualHost>

At mod_proxy configuration:

ProxyRequests Off

<Proxy *>
    Order deny,allow
    Allow from all
</Proxy>

The parties are key:

• Enable reverse proxying:

ProxyRequests Off

• Ensure that the downstream server will receive the correct "Host:" header. This option is off by default.
  

ProxyPreserveHost On

• Indicating how the proxy URI will convert converted as it passes through the Apache proxy server:

ProxyPass / http://www.ipv4foo.institution.org/
ProxyPassReverse / http://www.ipv4foo.institution.org/

• I configured these options for all, but can be configured for each VirtualHost.

<Proxy *>
Order deny,allow
Allow from all
</Proxy>

Finish it

This is not an "open proxy", because we restrict the reverse proxy to a single virtual host. The server serves files to the public, but only for the web sites listed. The configuration presented here facilitates the hosting of a large number of web sites, without having to actually store and synchronize the web site with a central server. The natural flow of proxy->core web server automatically keeps data synchronized. I advise to use of Apache HTTP Server high speed threaded model because of the load and number of connections.

Some resources

Apache2.2 information about mod_proxy. Show at http://httpd.apache.org/docs/2.2/