IPv6-ready kernel

Di distribusi Linux modern biasanya kernel sudah siap IPv6. Kemampuan IPv6 biasanya di compile sebagai modul. Akan tetapi sangat mungkin, modul tersebut tidak di load secara automatis,

Catatan: sebaiknya tidak menggunakan kernel seri 2.2.x lagi, karena IPv6 tidak update. Juga dukungan IPv6 di kernel 2.4.x tidak lagi sesuai dengan definisi RFC. Lebih di rekomendasikan menggunakan kernel seri 2.6.x atau yang terbaru sekalian.

Cek dukungan IPv6 di kernel yang berjalan

Untuk mencek apakah kernel yang berjalan mendukung IPv6, file berikut harus ada

/proc/net/if_inet6

atau kalau mau automatis dapat menggunakan script berikut

# test -f /proc/net/if_inet6 && echo "Running kernel is IPv6 ready"

Jika tidak jalan, kemungkinan modul IPv6 tidak di load.

Meload Module IPv6

Kita dapat mencoba me-load module IPv6 dengan menjalankan

# modprobe ipv6

Jika load tersebut berhasil, maka module IPv6 harusnya terdaftar dan dapat di test menggunakan script berikut secara automatis

# lsmod |grep -w 'ipv6' && echo "IPv6 module successfully loaded"

Harusnya jalan dengan baik

Catatan: unload module IPv6 saat ini masih belum jalan dengan baik. Mungkin akan terjadi crash kernel.

Load Module Secara Automatis

Alternatif lain adalah meload modul IPv6 secara automatis / on demand. Kita hanya perlu menambahkan kalimat berikut di file konfigurasi untuk kernel modul loader (biasanya /etc/modules.conf atau /etc/conf.modules atau /etc/modules) :

alias net-pf-10 ipv6  # untuk load IPv6 module on demand secara automatis

Juga kita bisa men-disable load IPv6 module secara automatis menggunakan kalinat berikut:

alias net-pf-10 off   # disable load IPv6 module on demand secara automatis

Catatan: di kernel 2.6.x, mekanisme load module di ubah. File konfigurasi di namakan /etc/modprobe.conf atau /etc/modprobe.d/*conf tidak lagi /etc/modules.conf.

Compile kernel dengan kemampuan IPv6

If both above shown results were negative and your kernel has no IP6 support, than you have the following options:

   Update your distribution to a current one which supports IPv6 out-of-the-box (recommended for newbies)

   Compile a new vanilla kernel (easy, if you know which options you needed)

   Recompile kernel sources given by your Linux distribution (sometimes not so easy)

   Compile a kernel with USAGI extensions

If you decide to compile a kernel, you should have previous experience in kernel compiling and read the Linux Kernel HOWTO.

A comparison between vanilla and USAGI extended kernels is available on IPv6+Linux-Status-Kernel. 4.1.3.1. Compiling a vanilla kernel

More detailed hints about compiling an IPv6-enabled kernel can be found e.g. on IPv6-HOWTO-2#kernel.

Note: you should use whenever possible kernel series 2.6.x or above, because the IPv6 support in series 2.4.x only will no longer get backported features from 2.6.x and IPv6 support in series 2.2.x is hopeless outdated. 4.1.3.2. Compiling a kernel with USAGI extensions

Same as for vanilla kernel, only recommend for advanced users, which are already familiar with IPv6 and kernel compilation. See also USAGI project / FAQ and Obtaining the best IPv6 support with Linux (Article) (Mirror). 4.1.4. IPv6-ready network devices

Not all existing network devices have already (or ever) the capability to transport IPv6 packets. A current status can be found at IPv6+Linux-status-kernel.html#transport.

A major issue is that because of the network layer structure of kernel implementation an IPv6 packet isn't really recognized by it's IP header number (6 instead of 4). It's recognized by the protocol number of the Layer 2 transport protocol. Therefore any transport protocol which doesn't use such protocol number cannot dispatch IPv6 packets. Note: the packet is still transported over the link, but on receivers side, the dispatching won't work (you can see this e.g. using tcpdump).

4.1.4.1. Currently known never “IPv6 capable links”

   Serial Line IP (SLIP, RFC 1055 / SLIP), should be better called now to SLIPv4, device named: slX

   Parallel Line IP (PLIP), same like SLIP, device names: plipX

   ISDN with encapsulation rawip, device names: isdnX

4.1.4.2. Currently known “not supported IPv6 capable links”

   ISDN with encapsulation syncppp, device names: ipppX (design issue of the ipppd, will be merged into more general PPP layer in kernel series 2.5.x)