PEEKS AND POKES: Serverside FSI applications in IPv6 environments

The latest releases of FSI Server 2 and FSI Cache 4 have introduced full IPv6 support. While running FSI Server and FSI Cache in IPv6 environments was possible before, customers and administrators had to accept certain restrictions. Addressing the applications was only possible using FQDNs, as IPv6 addresses were not evaluated when checking the licence information. The new releases now allow using IPv6 addresses as well as IPv4 and FQDNs. FSI Caches internal protection mechanisms against denial-of-service attacks are now also IPv6 aware which not only enables the Cache application to block traffic coming from an IPv6 source address but also allows specifying address ranges using IPv6 CIDR notation format.

For those new to the subject: If you want to use IPv6 addresses in URLs, you need to put the address in square brackets in order to allow the browser to correctly interpret the address. An FSI Server image request therefore might look like this:

This notation is also used in FSI Administrator when specifying the location of the FSI Server/FSI Cache to connect to.

Prior to the latest release, the above request would have resulted in an image containing an FSI Server watermark, as it was not possible to evaluate IPv6 addresses in FSI Server licences. As you can see, the image is now delivered without a watermark. In order to view the link above you must be in an IPv6 enabled network otherwise your browser will complain that the requested network is not reachable.

If you are migrating from an IPv4 network to an IPv6 network or if you just want to add IPv6 support to your running installation then there is a couple of things you might need to change. Presuming your network interface and routing is configured correctly, the Tomcat needs to be configured to listen for incoming IPv6 communication. To check the currently used address on a Linux server, please see the following example:

As you can see the Java process is listening on the IPv4 address only. In order to enable IPv6 you need to ensure that the Tomcat startup options do not include “” and also remove the address-Parameter from the connector section in the server.xml. Once you have done that and restarted the Tomcat your should see the following:

Your Tomcat/FSI Server is now ready to be accessed via IPv6, all that is left to be done is an AAAA record for your FQDN.

For more information see: Networking IPv6 User Guide