Author: Wido den Hollander

Using the internet on a IPv6-only network

At home I have native IPv6 via my ISP ZeelandNet since June 2014. Ever since I’ve been using the internet via IPv6 where possible.

Yesterday I thought it was time to create a IPv6-only VLAN + SSID at home and see what parts of the internet I could use while being on a IPv6-only network. No NAT64 or anything, just IPv6.

Linux router

I’m using a Soekris NET6501 with Ubuntu as my router at home. So I created a new VLAN and used that VLAN tag to create a new SSID on my Access Point.

Under Ubuntu I configured:

  • Radvd for Router Advertisements
  • Wide DHCPv6 Server for DNS servers

IPv6-only under iOS 9.1

I have an iPhone 5s and iPad Air 2 both running iOS 9.1 and I thought it was best to use these for testing the IPv6-only network.

They connected just fine! But the WiFi overview didn’t show any IP-Address. Seems that is still IPv4-only.

iOS 9.1 IPv6-only network

And ipv6-test.com showed that I had IPv6 connectivity only.

IPv6 test iOS 9.1

What works?

You might think that the internet breaks, but I think that already a lot of the large services work. A list of things which work:

  • Facebook / Messenger
  • Google: Search, YouTube, Maps and Gmail
  • NOS (Dutch news
  • Netflix
  • Apple Notifications
  • My own website and E-Mail
  • Various local sites I visit

What does not work?

Well, this could be a very long list. But there are certain services which should be highlighted for not supporting IPv6:

  • Twitter
  • Github
  • Apple App Store
  • Spotify
  • All Dutch Online banking

So yes, the biggest part of the internet does not work over IPv6. But most of the things work for me.

I’ll keep testing the internet using this IPv6-only SSID and I’ll probably keep bugging various admins to turn on IPv6.

Maximum amount of Docker containers on a single host

While playing with Docker I wanted to know how many containers I could spawn on a single system.

A quick for-loop told me that the maximum is 1023 containers on a single host:

Error response from daemon: Cannot start container 09c8f46b59ccc311e8d0352789db6debd0fa1df98186c5cda98583d762d48601: adding interface vetha5d205e to bridge docker0 failed: exchange full

The limitation here is the Linux bridging which can’t have more then 1023 interfaces attached. Specifically net/bridge/br_private.h BR_PORT_BITS cannot be extended because of spanning tree requirements.

wido@wido-desktop:~$ docker ps|wc -l
1024
wido@wido-desktop:~$

Although that says 1024 there is a header line, so we have to subtract one. That brings it to 1023.

wido@wido-desktop:~$ docker version
Client:
 Version:      1.8.3
 API version:  1.20
 Go version:   go1.4.2
 Git commit:   f4bf5c7
 Built:        Mon Oct 12 05:37:18 UTC 2015
 OS/Arch:      linux/amd64

Server:
 Version:      1.8.3
 API version:  1.20
 Go version:   go1.4.2
 Git commit:   f4bf5c7
 Built:        Mon Oct 12 05:37:18 UTC 2015
 OS/Arch:      linux/amd64
wido@wido-desktop:~$

Ubuntu and the changing MAC address with bonding

With the ‘new’ style for configuring bonding under Ubuntu your bond device will not always have the same MAC address across reboots.

For example, you configure your bond in the /etc/network/interfaces file:

auto p9p1
iface p9p1 inet manual
        bond-master bond0

auto p10p1
iface p10p1 inet manual
        bond-master bond0

auto bond0
iface bond0 inet manual
        bond-slaves none
        bond-mode 4
        bond-miimon 100
        bond-updelay 5
        bond-downdelay 5

During boot, both interface p9p1 and p10p1 will be hot-plugged under bond0. The first device to be plugged into the bonding device determines which MAC address the bonded device gets.

Due to hardware timing it might be p9p1 OR p10p1 which is the first. This behavior makes the MAC address selection inconsistent between reboots and that might cause problems with:

  • DHCP for IPv4
  • IPv6 with SLAAC (Stateless Auto Configuration)
  • DHCPv6

This has been filed as bug #1288196 with Ubuntu, but no fix from that side so far.

The solutions for now:

auto p9p1
iface p9p1 inet manual
        bond-master bond0

auto p10p1
iface p10p1 inet manual
        pre-up sleep 5
        bond-master bond0

This makes sure p10p1 always comes online 5 seconds after p9p1.

But you can also set a static MAC address for the bonding device:

auto bond0
iface bond0 inet manual
        hwaddress fe:80:12:04:6d:6f
        bond-slaves none
        bond-mode 4
        bond-miimon 100
        bond-updelay 5
        bond-downdelay 5

Choose what you prefer or works best in your situation.