Final IPv4 allocations; IPv6 readiness test; IPv6 world day

Final IPv4 allocations have been made today. Will this galvanize businesses to start moving to IPv6? We’ll see 🙂


If you’ve been following my “IPv6 at home” series, here’s a neat link to test your IPv6 readiness:


Finally, “World IPv6 day” will be on June 8th 2011. Google, Facebook, Yahoo, Akamai and Limelight will turn on IPv6 for 24 hours. Results should be interesting to see. If you’d like to prepare for World IPv6 day today, go on over to their official site.



IPv6 at home or office, part 4.1: 6in4 tunnel on Juniper ScreenOS firewall

This blog post is part of a series on ipv6. Part 4.0 describes requesting a Hurricane Electric tunnel; this part explains how to configure a Juniper ScreenOS firewall – SSG, ISG or Netscreen – to work with such a tunnel.

Sample environment

I am going to give an example based on ScreenOS 6.0.0 or later syntax. ScreenOS 5.4 is reported to support IPv6 6in4 tunnels, as well, though it does not expose the configuration to the web interface.

These settings can (almost) all be configured through the web interface. In the interest of brevity, I am going to show CLI commands instead.

Here are the interface names and addresses used in this example. In this example, I use the IPv6 documentation prefix. When configuring this, you get the real addresses from the Tunnel Details page.

External interface name: ethernet0/0, Untrust zone

Internal interface name: bgroup0, Trust zone

Tunnel interface name: tunnel.1, Untrust zone

Server IPv4 address:

Server IPv6 address: 2001:0db8:1:223::1/64

Client IPv6 address: 2001:0db8:1:223::2/64

Routed /64: 2001:0db8:2:223::/64

Anycasted IPv6 Caching Nameserver: 2001:0db8:1234::2

Enabling IPv6

This is the one step you must do from command line. Enter:

set envar ipv6=yes

and reboot. This will enable IPv6 features on your ScreenOS device.

Setting up the tunnel

The first step is to set up a tunnel interface that will allow you to encapsulate IPv6 packets in IPv4 packets.

set interface “tunnel.1” zone “Untrust”
set interface “tunnel.1” ipv6 mode “host”
set interface “tunnel.1” ipv6 ip <Client IPv6 address>
set interface “tunnel.1” ipv6 enable
set interface tunnel.1 tunnel encap ip6in4 manual
set interface tunnel.1 tunnel local-if <External interface> dst-ip <Server IPv4 address>
set interface tunnel.1 mtu 1480
unset interface tunnel.1 ipv6 nd nud
set interface tunnel.1 ipv6 nd dad-count 0
set route ::/0 interface tunnel.1 gateway <Server IPv6 address>

We’re creating the tunnel.1 interface, assign it to the “Untrust” zone, and give it its IP address, the “Client IPv6 address”.

Next we’re creating the tunnel itself, terminating on the external interface on one side and the Server IPv4 address on the other side.

We restrict MTU to 1480 as that is the largest packet that can go through without fragmentation, and disable Neighbor Unreachable Detection for good measure. I haven’t had issues with nud on, but others have.

Finally, create a default IPv6 route through the tunnel.1 interface, so our IPv6 traffic has somewhere to go.

Setting up IPv6 for the local network

Next, we’ll use the “Routed /64” that HE gave us for our internal network.

set interface “bgroup0” ipv6 mode “router”
set interface “bgroup0” ipv6 ip 2001:0db8:2:223::1/64
set interface “bgroup0” ipv6 enable
unset interface bgroup0 ipv6 ra link-address
set interface bgroup0 ipv6 ra preference high
set interface bgroup0 ipv6 ra other
set interface bgroup0 ipv6 ra transmit
set interface bgroup0 ipv6 nd nud
set interface bgroup0 ipv6 nd dad-count 0
set interface bgroup0 dhcp6 server
set interface bgroup0 dhcp6 server options dns dns1 <HE IPv6 Name Server>
set interface bgroup0 dhcp6 server enable

Here, we are giving the LAN interface an IPv6 address from the “Routed /64” range – in the interest of simplicity, I chose “1”. We then enable Router Advertisement so that local machines can receive IPv6 addresses from this interface.

We’re also setting the RA “other” bit and enabling DHCPv6 to give out HE’s IPv6 DNS server. Those two steps are optional: It’ll mean that Google’s IPv6-enabled services will resolve with both an IPv4 and an IPv6 address – otherwise, Google will only be reachable by IPv4.

Setting up an IPv6 firewall policy

As an example, here is a very simple policy that allows all outgoing IPv6 traffic, and denies all incoming IPv6 traffic. Adjust as fits your environment.

set policy from “Trust” to “Untrust”  “Any-IPv6” “Any-IPv6” “ANY” permit
set policy from “Untrust” to “Trust”  “Any-IPv6” “Any-IPv6” “ANY” deny

IPv6 at home or office, part 4.0:, IPv6 routers

This blog post is part of a series on ipv6. In part 1, I provided an overview of ipv6 and looked at Teredo, the technology built into Windows Vista; in part 2, I looked at AYIYA tunnels through aiccu, using sixxs net as a tunnel broker. Part 2.5 is a collection of useful ipv6 tidbits, and part 3 describes gogonet/freenet6 tunnels.

In part 4, I will describe the IPv6 tunnel I have been using all along since 2008: A Hurricane Electric 6in4 tunnel, typically terminating on a router, though it could be terminated on a PC, as well. I aim to break part 4 into chunks, each describing setup for a different make and model of router.

Provisioning of the tunnel

Make sure the router you will be using allows itself to be pinged from either “the Internet”, or at the least from HE’s server, currently66.220.2.74.

Sign up with Hurricane’s Electric service.

Once signed in, under “user functions”, choose “Create Regular Tunnel”.

Enter the IPv4 endpoint, and hit “Submit”. If you are a home user, your IPv4 endpoint is the public IP your ISP assigned to you, see

And you are done. Helpfully, the tunnel details page also allows you to get sample configurations for a variety of PC and router operating systems, including Linux, Windows, Cisco IOS, Juniper JunOS and Juniper ScreenOS.

Updating your dynamic IPv4 address

If you are in a home environment, your public IPv4 address may change from time to time. You can update it from the tunnel details page, or you can use’s ipv4 update page that is intended to be used from a script, for automatic updates.

Routers supporting 6in4 tunnels

Whether enterprise class or home router, here are some of the devices that support 6to4 with 6in4 tunnels today (February 2010). On the home router side, it’s clear that it is early days yet. Comcast’s ipv6 trials may change the competitive landscape here.


Any SSG or ISG firewall running ScreenOS 6.0.0 or later, as well as (with some limitations) Netscreen firewalls on ScreenOS 5.4.0. Part 4.1 describes the setup.

Any JunOS router – J-Series, M-Series, E-Series, T-Series, &c. All the way back to JunOS 9.1 if need be.

Any SRX firewall, with the caveat that SRX does not yet support ipv6 firewalling as of JunOS 10.1, though it does support ipv6 tunneling and routing.

EX switches do not support ipv6 tunnels yet, though the feature is road-mapped.


It’s the usual mess of IOS versions depending on model, paired with feature set. A very Cisco-savvy fellow over at the HE forums has an excellent breakdown. In a nutshell, IOS 12.4 or later should work, and you’ll need the right feature set.

Switch support for IPv6 is good. You’ll need to check model / IOS version / feature set here, too.


Apple Airport Extreme supports 6to4, and a one-click tunnel provisioning, too. This is the only home router that I’d be confident to use for IPv6 today, without needing to fear that a firmware update would break IPv6. Mainly because a firmware update did break IPv6, and Apple fixed it in v1.5. For this router, IPv6 is an officially supported feature.

[Update 2010-04-28] Comcast will use this router in their IPv6 dual-stack trials, as one of three choices.


Comcast will use the Netgear WNR3500 and Netgear WNR1000 in their IPv6 dual-stack trials. Whether these routers support 6in4 tunnels is unknown to me at this point.


[Update 2011-08-03: D-Link have updated their site with a list of devices supporting native IPv6] According to D-Link, the following router models support IPv6. Comcast are using the DIR-655 and DIR-825 in their native dualstack IPv6 trial.

D-Link IPv6 Certified Routers

  • DIR-601 Wireless N 150 Home Router (Hardware Revision A1)
  • DIR-615 Wireless N 300 Router (Hardware Revision E1)
  • DIR-632 Wireless N 8-Port Router (Hardware Revision A1)
  • DIR-655 Xtreme N Gigabit Router (Hardware Revision B1)
  • DIR-825 Xtreme N Dual Band Gigabit Router (Hardware Revision B1)
  • DHP-1320 Wireless N PowerLine Router (Hardware Revision A1)

Other IPv6 Certified Products

  • DHP-W306AV PowerLine AV Wireless N Extender (Hardware Revision A1)
  • DAP-1350 Wireless N Pocket Router and Access Point (Hardware Revision A1)
  • DAP-1360 Wireless N Range Extender (Hardware Revision B1)
  • DAP-2590 AirPremier N Dual Band PoE Access Point

D-Link state that their DSL modem routers, the DSL-2540B and DSL-2640B also support IPv6.

D-Link DGS-3200 and DGS-3600 switches officially support IPv6.


WRT610N, with reports that firmware updates break ipv6 support and that Linksys support is firm that ipv6 is not an officially supported feature. More testing is in order here, too.

[Update] A Linksys live chat operator tells me that native IPv6 is supported on the WRT610N, and that there is no official documentation for this. No word on tunnels. I have reached out to their press office to get details and will update if/when I get an answer.

[Update] The Comcast trial forums float the WRVS4400N as supporting tunneled and native IPv6.

Buffalo Technology

A “number of” their wireless products support ipv6. I have reached out to their press office to get details and will update if/when I get an answer.


FRITZ!Box 7270 (experimental “Labor” version)

I have reached out to their press office to get details and will update if/when I get an answer.

ipv6 at home: Comcast ipv6 trials

I’m admittedly late to the party with this, as it’s a January 27th announcement. Comcast is gearing up for public ipv6 trials starting in April, and they’re looking for guinea pigs trial users.

[Update 2010-02-26] I just received an email from Comcast. They’ll start ramping up 6RD trials nationwide. Dual-stack trials will be regionally limited. Trial users that do not have IPv6-ready equipment will receive equipment that is ready, including what Comcast calls a “gateway” (home router). They may start contacting volunteers in a month, and expect to start some of these trials within 3 months.

There’ll be four total phases to the trial:

Q2 2010

IPv6 tunneled over IPv4 using 6RD. If you’re using one of the tunnel methods I describe in this blog today, you’re familiar with this.

Native dual stack. You’ll have both an ipv4 address and ipv6 addressing natively. Your router will need to support ipv6.

Q3 2010

IPv4 tunneled over IPv6, dubbed “Dual Stack Lite”. You’ll have a private IPv4 address, and use a tunnel over IPv6 to share one public IPv4 address with several other subscribers. Interesting approach.

Business class dual stack

In other “late to the party” news, Google turned up ipv6 on youtube sometime in January. Full production, caused a big spike in v6 traffic, and it seems to be working just fine.

ipv6 addressing – there is no NAT, and “renumbering needs work”

Addressing is a big deal with ipv6. For people coming from ipv4, wrapping one’s head around ipv6 addressing can be hard.

This post is a response to the comments discussion in the Standalone Sysadmin blog post urging uptake of ipv6. In the comments, we see people concerned with the fact that ipv6 addressing gives a public, routable address to every last PC, server and printer – and suggestions that this could be resolved by deploying ULA (Unique Local IPv6 Unicast Addresses) per RFC4193 – it’ll be just like your current RFC1918 space!

Actually, it won’t. ULA is not the solution. Every machine that needs access to the Internet will be on a routable, public address. That’s only scary from a management perspective – and that’s the TL;DR. Read on for the justification of that statement.


ULA addressing is addressing per RFC4193. It is different from RFC1918 in some ways, and it shares a few characteristics with RFC1918.

ULA is different from RFC1918 in that the addresses are meant to be unique. This is achieved by using a Pseudo-Randomly derived “Global ID” as part of the site prefix. The RFC goes into detail – at length – as to how that PRNG generation is supposed to work. In practice, you still have a very small chance of collision. ULAs were never meant to be registered in any way – SixXS gives you a registration page anyway, just to avoid that small chance of overlap.

ULA is similar to RFC1918 in that ULA address space is “not expected to be routable on the global Internet”. This translates to a requirement to filter out ULA space at the BGP border router, and for all exterior routing protocols to “ignore receipt of and not advertise” ULA space. See section 4 of the RFC for details.

ULA is different from RFC1918 in that ipv6 does not offer NAT  (though arguments are being put forth that ipv6 NAT may be beneficial). Wait, I hear you say, how is that a difference between ULA and RFC1918? That’s a difference between ipv6 and ipv4! To which I say: True enough. That difference impacts how these addresses can be used, would be a better way to put it. You can put a PC on an RFC1918 address, and it can still get to the Internet, through a Many-to-One source NAT. You can put a server on an RFC1918 address, and it will still be reachable through a static one-to-one NAT. You cannot do any such thing with a machine that has only a ULA address. That machine will be unable to get to the Internet, and vice versa.

[Edit 2011-02-03: NAT is with us again, in the form of NAT66. Note that it is designed to translate one /48 prefix into another /48 prefix. I am still not a great fan of this idea, as the application challenges remain. If you’ve ever tried to NAT h.323 or sip and found that your firewall doesn’t _quite_ speak your version of that protocol, you know what I speak of. Designing an IPv6 network without the need for NAT66 is, in my opinion, far preferable]

That doesn’t mean that ULAs are useless. They are meant to allow local machines to communicate locally – combined with the idea of DHCP-PD, this can be a way to handling renumbering. RFC4864 was written specifically to address concerns about manageability of local IPv6 space.

Let me speak to this new ipv6 world where every machine has a routable public address from a few perspectives.

Application perspective

Doug Maxwell says:
1) It’s always routing
2) No NAT is good NAT
3) Sh^t don’t work

NAT is the bane of your applications. If you’ve ever tried getting SMB or VoIP through NAT, you know what I speak of. Any application that references an IP address in L7 – whether that’s a good idea or no, it happens – is going to be hurting. Many-to-one NAT will be hurting P2P applications, which ipv4 proposes to resolve by using port forwards, which don’t scale. It’s a nightmare.

Interestingly enough, the biggest boost to public (as opposed to governmental) ipv6 uptake has been from a popular p2p application starting to support ipv6. Go figure.

No NAT is a good thing from an application perspective. It also helps to make inter-partner VPNs so much easier to set up.

Security perspective

Repeat after me: NAT is not a security solution.

It may be fairer to say: The security gained by many-to-one source NAT is a side effect.

It is your firewalls’ (perimeter and internal, if you have any internally) job to control which traffic may reach your internal network. If your rulebase looks like this:

Internal-LAN to Any on http/https/ping : Allow
Any to Internal-LAN on Any : Deny

then your Internal-LAN is going to be just as secure on public space – ipv4 or ipv6 – as on private space. If you can’t get to it, you can’t get to it, no matter whether the address is routable.

You can also think about this from a server perspective: Say you have a web server on, and you NAT it to a public address. Your firewall rulebase will look like this:

Any to Public-WWW on http: Allow

Whether this Public-WWW address is now going to be NATed to, or just routed to the server, makes absolutely no difference from a security perspective.

Management perspective – “renumbering needs work”

Managing your address space needs considerably more forethought in ipv6 than in ipv4. ipv6 is new now, but it’ll be an “old hat” before you know it – and then you’ll be shopping around for the best deals on ISP connectivity, just as you do now with ipv4. The idea of needing to renumber absolutely everything when you switch ISPs is not pleasant. RFC4864 has a few suggestions on how to handle that – none of which may be really workable in your situation.

There is one “easy” solution to this mess: Get your own site address space(s) assigned to you by your local RIR, whether that’s ARIN or somebody else. Then use that space in perpetuity, regardless of the IPS(s) that provide your bandwidth. Unfortunately, the ipv6 early adopter days are over, and the ipv4-has-run-out days are not yet here. As a result of which, ipv6 eligibility is tied to ipv4 eligibility: You can get your own ipv6 address space if either a) you already own ipv4 space and can show that you use it efficiently or b) you are eligible to receive ipv4 space. As of early 2010 looking at ARIN rules, that means you’d have to be eligible for an ipv4 /22, and currently use a /23 worth of ipv4 public space efficiently. That’s a tough hurdle to jump over.

As a manager, you’ll want to have your people fight tooth and nail for that directly assigned space. It is the by far most cost-effective and most lasting solution to renumbering concerns.

If that is not an option, and you need ipv6, you need to pay a lot of attention to IP Address Management. The old “spreadsheet kept by the IT dept” method will no longer work. What you’re looking for is strong asset management – DHCP, DNS and ACLs populated by a backend asset database. The marketplace will create these solutions as ipv6 uptake gets under way. Infoblox is one company to watch in this space, though they do not tie into ACL generation.

The best advice I can give is to plan for a renumbering scenario if you cannot get your own address space. Evaluate IAM solutions and network management solutions. Have your people run through a dry-run of renumbering to uncover areas that may have been overlooked, such as application settings.

A few basic configuration choices will make renumbering easier:

– Use DHCPv6 to assign addresses to not just workstations, but also servers. Servers will have their address bound by MAC address – this is where your IAM comes in handy

– Use DNS in your configurations wherever possible – avoid the use of static addresses where feasible and where performance allows it

– Use a network management application that allows you to change the addressing and configuration of your routers and switches quickly and easily

I am not a big fan of DHCPv6 prefix delegation, outside of a provider-to-consumer relationship, that is. DHCPv6 prefix delegation is meant to work with stateless auto-configuration, for routers that have one upstream link and one LAN link. Great in a provider environment, not so great in an enterprise environment.

Lastly, let me share some useful resources: A draft RFC proposing a renumbering methodology without the “flag day”, and a whitepaper from January 2009 looking at IPv6 renumbering, the current challenges and options.

ipv6 at home, part 3: gogonet tunnels, freenet6

This blog post is part of a series on ipv6. In part 1, I provided an overview of ipv6 and looked at Teredo, the technology built into Windows Vista; in part 2, I looked at AYIYA tunnels through aiccu, using sixxs net as a tunnel broker. Part 2.5 is a collection of useful ipv6 tidbits, and this part 3 gets back to the original plan: Exploring ipv6 connectivity options – in this case, the tunnel offered by gogo6 (formerly Hexago) at gogonet.

Tunnel overview

freenet6, the tunnel service offered by gogo6, uses TSP (Tunnel Setup Protocol) to determine the best tunnel type. It offers IPv6-in-IPv4 tunnels in Native mode (direct connection to a public ipv4 address, no NAT), IPv6-in-IPv4 tunnels in NAT traversal mode (also called IPv6-in-UDP-is-IPv4; this is what you’ll most likely use), and even IPv4-in-IPv6 tunnels (using DSTM, used to reach ipv4 resources if you have an ipv6 address but no ipv4 address – not a very likely scenario at this point in time).

The tunnel service is delivered through gateway6, an incredibly intuitive and easy-to-use client. Both anonymous and authenticated tunnels are available. An anonymous tunnel will provide ipv6 access for the machine the gateway6 client is installed on; an authenticated tunnel gives you a routable /56 network to hand out to the rest of your network.

Setting up an anonymous tunnel

Install the gateway6 client; launch it; leave everything at default; hit “Connect”.

Test your connection by browsing to

In this mode, your assigned ipv6 address will change as your ipv4 address changes.

I should spruce this paragraph up by adding a screen shot of the gateway6 client with all default settings, but it feels gratuitous. This method of connection is hands-down the easiest way to get ipv6 connectivity that you are likely to find.

Setting up an authenticated tunnel

Sign up with freenet6. This is separate from the gogonet account you need to even download the client.

Install the gateway6 client.

Change the “Gateway6 address” to be “”.

Set the client to “Connect using the following credentials”, and enter your user name and password with

On the off-chance that a tunnel endpoint would default to clear-text authentication, you can go to the “Advanced” tab and change your Tunnel Authentication Method to either PASS DSS 3DES1 or Digest MD5.

Hit “Connect” and test your connection by browsing to

In this mode, your assigned ipv6 address will remain static, even if your ipv4 address changes.

Setting up routing to the rest of your network will assign a /56 prefix to you on an authenticated tunnel, if you request it.

The simplest way to set this up is:

On the “Advanced” tab, check “Enable Routing Advertisements”. Choose the LAN interface that will serve the ipv6 prefix to the rest of your network. Leave the prefix length at /64.

Hit Connect, and check the “Status” tab – you’ll see your assigned /56 prefix. Of which you are currently using the first /64 – if you have further subnets, you can start assigning more /64s and routing them to the machine that runs the gateway6 client.

Advanced options – running on a router, reverse DNS delegation

Through changing the gw6c.conf file, you can use the gateway6 client to request configuration for a router; and you can request delegation of your ipv6 prefix to your own name server for RDNS (PTR) resolution.

RDNS delegation is set up by simply changing the “dns_server=” entry.

You can run the gateway6 client as a “proxy”, in which mode it will request configuration information for a router. This is described in the gogonet forums. You’d want to set the requested prefix length to /56, not /48 – otherwise, no changes should be necessary.

The provided template outputs configuration for a Cisco router. You can take the relevant information out of the Cisco config file and use it with a Juniper device, or DLink, Apple, any router that supports 6-in-4 (protocol 41) tunnels. You could also write your own template script to output the information in the format your router requires – it’s a simple batch file.

Final thoughts

If you want ipv6 connectivity, and you do not intend to gain it through your router, gogonet should be your first stop. The gateway6 client shows that gaining ipv6 connectivity, and setting up routing to everything else in your network, does not have to be complicated, or involve lengthy command-line sessions.

If you want to terminate your tunnel on a router, give Hurricane Electric a look. Their tunnel setup does not require a client running on a PC – on the other hand, that means it won’t present the router configuration commands to you on a silver platter, either. Consider also that freenet6 has a somewhat patchy record when it comes to reliably handing out your delegated prefix: In the past, prefix numbers would change, and that messes with your router setup and your RDNS.

I had, when I first started writing this series, deliberately placed behind Teredo and SixXS: I knew it was going to be far easier to set up than those other two, and wanted to progress from “complicated” to “easy” as the series went on. I had not counted on getting stuck quite so hard on routing with the SixXS aiccu setup. In hindsight, covering the easiest method first might have been cleverer.

ipv6 at home, part 2.5: Google, DHCPv6, speed tests, troubleshooting, various

This blog post is part of a series on ipv6. In part 1, I provided an overview of ipv6 and looked at Teredo, the technology built into Windows Vista; in part 2, I looked at AYIYA tunnels through aiccu, using sixxs net as a tunnel broker. I also got stuck for a very long time on trying to use Windows as a router for an ipv6 subnet on that setup, and ultimately failed to make that work.

Part 2.5 is going to be an in-between – a collection of ipv6-related tidbits that will, hopefully, be useful, but have no particular cohesion.

Google services on ipv6

Back in January, Google announced that they had moved a number of their services to be multi-homed. To avoid causing issues for people with Vista that didn’t have functioning ipv6 connectivity, this is an opt-in service. That is achieved by using a DNS server that peers with Google for ipv6 addresses.

Unless you work for an ISP, you are not going to peer your own servers with Google. However, several tunnel brokers, including Hurricane Electric and sixxs, offer DNS servers that can serve up Google ipv6 addresses.

Here’s an example nslookup:

Server:  UnKnown
Address:  2001:470:20::2

Non-authoritative answer:
Addresses:  2001:4860:b002::68

As you can see, both A (ipv4) and AAAA (ipv6) records are being returned. In order for Vista to use the ipv6 address, you need to use the ipv6 address of the DNS server. If you query DNS over ipv4 and get both A and AAAA records, Vista will prefer an ipv4 address.

You can test which address is going to be used by running “ping”, which will show the numerical address that the OS is trying to reach.


If you are using a software tunnel such as AYIYA over aiccu, then you can set the DNS server to be used manually, through the Control Panel. If you are using an ipv6-capable router or firewall, however, you can send out that information over DHCPv6.

Cisco has a clear and concise paper on DHCPv6. From an implementation standpoint, it is very simple: Decide whether DHCPv6 is only going to serve DNS addresses, or whether it is going to handle all ipv6 address assignment, too. Then set flags for your RA (Router Advertisement) Configuration: “O” (“Other Parameters”) if RA handles addresses and DHCPv6 handles DNS, or “M” (“Managed”) if DHCPv6 handles addresses and DNS.

An RFC draft dated July 2005 suggests to expand RA to be able to hand out DNS server addresses without the need for DHCPv6. That draft has not yet been adopted, and I have yet to see an implementation in a major vendor’s routing OS.

[Update 2008-08-02] Jeremy points out that the above statement about implementation being “very simple” is rather brash. He’s correct, and explains the differences between Windows and Linux/Unix in this regard in his company blog. With lots of references to “dueling RFCs”, fun. For a broader view of ipv6 and its real-world applications, and a much more in-depth view than “okay how do I get this to work at home anyhow”, definitely do follow his blog.

Speed Test

If you’d like to compare your ipv6 speed to your ipv4 speed, you can do so through an ipv6 speed test offered by the University of Maine. The test can actually run in both ipv6 and ipv4, which makes it useful for comparison. is reachable through ipv6 as well – if you can find a suitably large file there, it could serve as a measure of download speed over ipv6.


This may have to be a “paragraph-in-perpetual-progress”. A few of the tools I found useful are:

Wireshark, in case you need to see what is happening to your ipv6 packets – are they leaving on the interface you think they should be leaving on, do you see return packets?

netsh is full of useful commands in its “interface ipv6” context, among them:

show route – does that just, shows you the ipv6 routing table

show siteprefixes – you’ll get a list of all the ipv6 prefixes (networks) configured on your machine

show prefixpolicies – you’ll see a list of which prefixes are preferred in which order. This is explained in more detail at ipv6 Day. Note that my own attempts to “fiddle with” prefix policy left me in a state where Vista would not function for ipv6 traffic at all.

reset – resets all ipv6 settings to default. Really useful if you’ve done a little too much fiddling. Needs a reboot.

show addresses – will show you the ipv6 addresses and their lifetime

show interfaces – configured interfaces and their up/down state

ipconfig /release6 and ipconfig /renew6 can be used to release/renew RA or DHCPv6 addresses

Turning off unused tunnel interfaces

Windows comes with built-in Teredo, ISATAP and 6-to-4 tunnel interfaces. These can become a distraction when configuring an alternative way to access ipv6, such as through your router or a third-party tunnel application.

Courtesy of ipv6 Day comes a description of registry settings to turn these off. There are a lot of possible combinations, including some that will turn off ipv6 entirely, which can come in handy in corporate environments.

The TL;DR for turning off all Windows built-in tunnels is:

  • In regedit, navigate to HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\tcpip6\Parameters\
  • Create a DWORD called DisabledComponents
  • Set it to “1”
  • Reboot

ipv4 exhaustion counters

Hurricane Electric, my preferred tunnel broker, offers a number of widgets and applications to keep track of ipv4 address space exhaustion. That includes Vista / Win 7 gadgets, Google Desktop and iGoogle gadgets, iPhone/iPod touch apps, and a web widget.

The “days remaining” are to be taken with a grain of salt. 676 days to complete ipv4 exhaustion! (As of August 2nd 2009) Actually, what is likely to happen is that we’ll see ipv4 space become more and more expensive, to the point where it is no longer economically feasible to own large portions of it just for access purposes – we’ll see hosting companies running it for decades, and your typical office running on v6 with a way to reach v4 over a tunnel. The reverse of today’s situation – eventually.

ipv6 certification

[Update 2009-08-06 – More detail on DNS requirements for this cert program]

Hurricane Electric also offers a fun ipv6 certification. What’s interesting about it is that it’s almost completely results-based. The first few levels (“Newbie” and so on) are just a questionnaire, but to reach the coveted “Sage” level, it’ll be doing real tasks, such as sending/receiving SMTP email over ipv6.

Achieving this entirely from home has one more than one challenge – you need a DNS server that will let you set AAAA records, will act as delegation for ipv6 PTR records, has its own AAAA entry and will respond to ipv6 queries, and you will need ipv6 glue for your DNS server at the TLD. There are a number of free ones available. These will let you set AAAA records, and usually also function for RDNS delegation. None of them are reachable over ipv6. A combination of, and a BIND server on your machine will get you all the way to “Guru”, but you won’t get “Sage” that way, as you’ll be missing the TLD glue.

The certification tests use the same domain you start out with throughout, or a subdomain thereof. If you want “smooth sailing”, choose a domain you own on a registrar that supports ipv6 glue.

It’s a worthwhile exercise in that you’ll find that ipv6 connectivity itself is really not the issue – finding real-world applications that support ipv6 is the larger challenge. You’ll also learn more about ipv6 DNS than you truly ever wanted to know.

ipv6 address space – think about registering yours

If you are involved in a corporate networking group, you may want to think about how you are going to handle ipv6 space. Traditionally, you get your address assignments from your ISP. This creates an amount of pain when moving ISPs. In ipv4, that’s public-facing addresses, while the internal network can stay untouched. In ipv6, everything uses public addresses – no more NAT (pending discussion, there are address translation efforts underway for ipv4/ipv6 translation – which doesn’t change the situation w/ regards to your ipv6 space). That means an ISP move could potentially require you to renumber everything, down to the last printer and desktop.

You can plan for this, by avoiding static assignments wherever possible, and always thinking about “how would I switch this to an entirely different subnet if I had to?” every step of the way.

Or, if you qualify, you can get a direct assignment of ipv6 space from ARIN. This used to be trivially easy as an “early adopter”, but that policy has been discontinued. Now, you need to be either a) eligible for direct ipv4 assignment (that’s getting tougher and tougher by the month) or b) already have a direct ipv4 assignment, and show that you use it efficiently.

It’ll be interesting to see how this policy evolves as ipv4 space becomes ever scarcer – will ARIN just stop assigning v6 space directly to end users, or will we see policies that are not tied to v4 eligibility?

[Edit 2009-08-02]

As Jeremy points out in a comment, ULA space (Unique Local Address as per RFC4193) is a the solution to receiving address space from your ISP, but wanting to avoid the pain of needing to re-do addressing of your entire network when moving ISPs. As long as the devices you give these addresses to do not need connectivity to the Internet, that is: As per the RFC, “They [the ULA addresses] are not expected to be routable on the global Internet”. In practice, that translates into a requirement to filter out ULA space at the BGP border router. SixXs has a page to register ULAs. As they point out, while there is no requirement to register ULAs, collisions (which are not very likely but can happen) can be dealt with by registering ULAs anyway.