Supporting IPv6 on a Linux Server Node

The current version of the IP protocol, IPv4, has proved to be robust, easily implemented, interoperable and has stood the test of scaling to the size of today's Internet, most of which uses IPv4—now nearly 20 years old. IPv4 has been remarkably resilient in spite of its age, but it is beginning to have problems. The initial design of IPv4 did not take into consideration several issues that are of great importance today, such as a large address space providing a solution for the address crunch problem, mobility, security, autoconfiguration and quality of service.

To address these concerns, the Internet Engineering Task Force (IETF) has developed a suite of protocols and standards known as the IP version 6 (IPv6), which incorporates many of the concepts and proposed methods for updating IPv4. Some of the IPv6 features include a new header format, a larger address space (128 bits), an efficient and hierarchical addressing and routing infrastructure, the availability of stateless and stateful address security, built-in security, better support of mobility and a new protocol for neighboring node interaction. As a result, IPv6 is not only going to fix a number of problems in IPv4, it also will add many improvements. IPv6 is expected to replace IPv4 gradually, with the two coexisting for a number of years during a transition period.

There are two main IPv6 implementations for Linux: the implementation that comes as part of the Linux kernel and the USAGI (UniverSAl playGround for IPv6) implementation. The USAGI Project works to deliver a production-quality IPv6 protocol stack for Linux, tightly collaborating with the WIDE, KAME and TAHI Projects. It is run by volunteers from various organizations contributing to the Linux and the IPv6 communities via the delivery of the IPv6 protocol stack. Currently, there are many efforts in the different distributions teams, and USAGI is trying to unify them so that there is one IPv6 implementation for all Linux distributions.

For the purpose of this article, we use Linux kernel 2.4.5 from kernel.org. We first show how to build a kernel with IPv6 support, then how to upgrade the basic networking software to support IPv6 and finally, how to connect your IPv6-enabled server to the IPv6 Internet using the services from the www.freenet6.net Project.

The first step is to download the Linux kernel from kernel.org and uncompress it:

tar -xzf linux-2.4.5.tar.gz

You will have a directory called linux. You need to move this directory into /usr/src and rename it linux-2.4.5 to reflect the kernel version. Next, you need to create a link to the 2.4.5 source directory:

ln -s /usr/src/linux-2.4.5 /usr/src/linux

cd /usr/src/linux
make xconfig (or menuconfig)

"Prompt for development and/or incomplete
   code/drivers"    YES

Figure 1. Enabling Support for Experimental Features

Then go to the Networking Options. There you will enable the IPv6 protocol:

IPv6 Protocol (EXPERIMENTAL)    YES

Figure 2. Linux Kernel IPv6 Configuration

This is all the configuration you need at the kernel level. Next, you should save this configuration and exit by clicking on the Save and Exit button (see Figure 3). This will create a .config file in /usr/src/linux, which is the kernel configuration file. Now you are ready to compile the kernel by following these steps:

make clean
make dep
make bzImage

Figure 3. Saving the Configuration

The result will be a new kernel image created in /usr/src/linux/arch/i386/boot/. If you added other features as modules you need to compile and install the modules by applying:

make modules
make modules_install

At this point you need to copy the new IPv6-enabled boot image to /boot:

cp /usr/src/linux/arch/i386/boot/bzImage
    /boot/bzImage.ipv6

cp /usr/src/linux/System.map \
/boot/System.map-2.4.5-ipv6
ln -fs /boot/System.map-2.4.5-ipv6 /boot/System.map

image=/boot/bzImage.ipv6
label=linux_ipv6
root=/dev/hda1 # change this to reflect your own
               # partition
read-only

/sbin/lilo

Figure 4. ifconfig Loopback