Subject: About IPv6 private address

From: blue <[email-masked]>
Date: Mon, 04 Feb 2008 10:59:57 +0800

Hi,

I want to ask if there's any reserved private IPv6 address? I know 
RFC4193 has defined Unique Local IPv6 Unicast Addresses, which is used 
to replace deprecated site-local address. However, in user's 
perspective, a device will need a well-known address, such as 
192.168.1.1 in IPv4, for a customer to connect to without any 
configuration. In RFC 4193, the address' "global ID" is generated 
randomly, and the address could not be known in advance.

After examing all the special purposed IPv6 address, I could not find 
one for this kind of purpose.

Thanks.
BR,
Yi-Wen

---

From: Fred Baker <[email-masked]>
Date: Mon, 4 Feb 2008 05:25:19 +0200

On Feb 4, 2008, at 4:59 AM, blue wrote:

> RFC4193 has defined Unique Local IPv6 Unicast Addresses, which is  
> used to replace deprecated site-local address. However, in user's  

No, there is no such "well known" address. Are you thinking of  
configuration purposes, such as a Linksys box uses - you http the  
magic address and configure it?

---

From: Fred Baker <[email-masked]>
Date: Mon, 4 Feb 2008 06:21:03 +0200

This is straight off the top of my head, without a lot of thinking.  
But suppose the device took a random (as random as it could come up  
with) ULA and decided to use it locally, and became the "router",  
which is to say, issued an RA? That would be needed for the host to  
form an address anyway. The host could then connect to the local  
router, whose address it by definition knows (it is the only foreign  
address in its neighbor database). The router could discard the ULA  
after configuration completed and it had a prefix issued by its ISP.

Do other folks have a suggestion?

On Feb 4, 2008, at 5:45 AM, blue wrote:

> Fred Baker wrote:
>>> I want to ask if there's any reserved private IPv6 address? I  
>>> know  RFC4193 has defined Unique Local IPv6 Unicast Addresses,  
>>> which is  used to replace deprecated site-local address. However,  
>>> in user's  perspective, a device will need a well-known address,  
>>> such as  192.168.1.1 in IPv4, for a customer to connect to  
>>> without any  configuration. In RFC 4193, the address' "global ID"  
>>> is generated  randomly, and the address could not be known in  
>>> advance.
>>
> Dear Fred:
> Yes, users need to configure our device via http, and if there's no  
> well-known IPv6 address, how do users know which address to connect  
> to? I have thought about a pre-configured link-local address;  
> however, browsers such as Firefox does not support link-local  
> address. Any suggestions?
>
> BR,
> Yi-Wen

---

From: "Erik Kline" <[email-masked]>
Date: Sun, 3 Feb 2008 21:17:10 -0800

I think that's pretty clever, actually.  It doesn't have to advertise
itself as a default router which, per
http://tools.ietf.org/html/rfc2461#section-6.2.3 if I read it
correctly, isn't hard.  The device could include a ULA generating
implementation or always use a well-known ULA (chosen by the
manufacturer).  It certainly warrants more thought, but it seems cool
to me so far.

---

From: Fred Baker <[email-masked]>
Date: Mon, 4 Feb 2008 07:20:46 +0200

On Feb 4, 2008, at 7:17 AM, Erik Kline wrote:

> http://tools.ietf.org/html/rfc2461#section-6.2.3

That would be http://tools.ietf.org/html/rfc4861#section-6.2.3, right?

:-)

---

From: "Erik Kline" <[email-masked]>
Date: Sun, 3 Feb 2008 21:32:31 -0800

> That would be http://tools.ietf.org/html/rfc4861#section-6.2.3, right?

That's what I get for not stopping to think carefully and clearly (and
not double-checking everything)!  Thanks!  :)

---

From: Mark Smith <[email-masked]>
Date: Mon, 4 Feb 2008 20:58:39 +1030

On Mon, 04 Feb 2008 10:59:57 +0800
blue <[email-masked]> wrote:

> 192.168.1.1 in IPv4,

As a minor data point, while 192.168.1.1 is well used, it isn't a well
known address that you can always use. I deal with a few different
pieces of ADSL CPE at work, and on occasion I've also seen
192.168.0/24, 192.168.2/24, and on some occasions, to avoid colliding
with existing nodes already using 192.168. [0-2]/24, it jumps to a
different subnet within 192.168.[0-255] on every boot. For those
devices you have to lookup the default gateway address announced via
DHCP.

Regardless, having the customer type in a name, not an IPv4 or IPv6
address, is far more user friendly.

> for a customer to connect to without any

---

From: Remi Denis-Courmont <[email-masked]>
Date: Mon, 4 Feb 2008 14:20:30 +0100

> one for this kind of purpose.

In principle, fixed link-local address are possible. Though you'd need to

know the interface identifier on the client, which makes this, as you

noted, not very workable a solution.

I note that this, in any case, can only work for a gateway device. Any

other IP-based appliance (networked printer, networked Hi-Fi, networked

toast-maker) can anyway not use a fixed address, and has to resort to

multicast discovery.

So... in the gateway case, you could probably use a fixed local DNS name

provided by the router DNS cache, that resolves to the ULA of the router.

This means the router needs to have local DNS caching server. Or then, as

already proposed, you can use a fixed ULA, but that kind sucks as it kills

the whole idea UNIQUENESS of ULA.

-- 

Rémi Denis-Courmont

http://www.remlab.net

---

From: Christian Huitema <[email-masked]>
Date: Mon, 4 Feb 2008 23:53:42 -0800

> One complaint I have heard several time is, the notation is merely a de
> facto standard extension of getaddrinfo et al. Also, as far as I know,
> Windows does not implement it and for a reason:
>
> fe80::216:41ff:fee1:b7fd%"Network Adapter" would not be very convenient
> and
> fe80::216:41ff:fee1:b7fd%1 (if 1 is the scope ID is not very
> meaningful).

Where did you get that notion? Sitting in my home network, my laptop can easily ping another computer in the same network, as in:

C:\Users\huitema>ping flocon

Pinging flocon [fe80::d515:c438:f880:85f2%13] from fe80::302f:358b:14f2:c78d%13
with 32 bytes of data:
Reply from fe80::d515:c438:f880:85f2%13: time=1ms
Reply from fe80::d515:c438:f880:85f2%13: time=1ms
Reply from fe80::d515:c438:f880:85f2%13: time<1ms
Reply from fe80::d515:c438:f880:85f2%13: time<1ms

Ping statistics for fe80::d515:c438:f880:85f2%13:
    Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
    Minimum = 0ms, Maximum = 1ms, Average = 0ms

Name resolution is performed using LLMNR, returning IPv6 local addresses. Simple and easy.

-- Christian Huitema

---

From: Remi Denis-Courmont <[email-masked]>
Date: Tue, 5 Feb 2008 08:18:54 +0100

On Tue, 5 Feb 2008 10:19:30 +1300, Nathan Ward <[email-masked]> wrote:

> Longer term, it seems as though applications should support link local

> addresses. Has there been any documentation that disagrees with that?

> Safari reports link local addresses with the interface specified as

> being invalid (ie. %en1 at the end = 'invalid').

fe80::216:41ff:fee1:b7fd%"Network Adapter" would not be very convenient and

fe80::216:41ff:fee1:b7fd%1 (if 1 is the scope ID is not very meaningful).

In any case, while applications should try to support these addresses, we

need to keep in mind that:

- the scope ID depends is hardware- and OS-dependant, if not boot sequence

dependant, hence cannot be used in a "for-dummies" documentation,

- application that rely on inet_pton(), inet_ntop() - and there may be

valid reasons - are kinda screwed,

- the scope being system-specific, cannot be exchanged accross the network:

think HTML hyperlinks, SDP c= lines, FTP control connection... and most

importantly DNS AAAA queries, so they are off limited practical usability

in any case.

I really think a home gateway ought to provide a ULA prefix, at least if it

cannot get any valid prefix from its upstream.

-- 

Rémi Denis-Courmont

http://www.remlab.net

---

From: Mohacsi Janos <[email-masked]>
Date: Tue, 5 Feb 2008 09:35:11 +0100 (CET)

On Tue, 5 Feb 2008, Nathan Ward wrote:

> On 4/02/2008, at 3:59 PM, blue wrote:
>
>> Hi,
>> 
>> I want to ask if there's any reserved private IPv6 address? I know RFC4193 
>> has defined Unique Local IPv6 Unicast Addresses, which is used to replace 
>> deprecated site-local address. However, in user's perspective, a device 
>> will need a well-known address, such as 192.168.1.1 in IPv4, for a customer 
>> to connect to without any configuration. In RFC 4193, the address' "global 
>> ID" is generated randomly, and the address could not be known in advance.
>> 
>> After examing all the special purposed IPv6 address, I could not find one 
>> for this kind of purpose.
>
> My opinions;
>
> addresses. Has there been any documentation that disagrees with that? Safari 
> reports link local addresses with the interface specified as being invalid 
> (ie. %en1 at the end = 'invalid').

This would rather confusing to users:

"server is reachable via fe80::123:45ff:fe67:89ab%eth0, if you use Linux 
with one ethernet interface"
"server is reachable via fe80::123:45ff:fe67:89ab%en0, if you use MacOS X"
"server is reachable via fe80::123:45ff:fe67:89ab%en1, if you use MacOS X
with wireless"
"server is reachable via fe80::123:45ff:fe67:89ab%fxp0, if you use *BSD 
with Intel card"
etc.

I think link-local on the user side can be used for communication:
- for diagnostic purpose
- for administrative purpose
- for users if link-local address discoverd automaticaly and they don't 
have to type in.

Administrators can cope with Ethernet interface name or number, but you 
cannot expect this from ordinary users.

Best Regards,
 		Janos Mohacsi

---

From: Remi Denis-Courmont <[email-masked]>
Date: Tue, 5 Feb 2008 09:40:03 +0100

On Mon, 4 Feb 2008 23:53:42 -0800, Christian Huitema

> Where did you get that notion?

The full Windows name of a network device, while it makes more sense to

normal people, is too long to fit after the percent sign.

I know what my Windows box "Ethernet adapter Local Area Connection", and,

because I am Linux-literate, I know what my Linux box "eth0" is. As it

happens, I don't know the corresponding numerical scope/interface

identifier of either of them.

fe80::216:41ff:fee1:b7fd%eth0 means something to me.

fe80::216:41ff:fee1:b7fd%"Ethernet adapter Local Area Connection" would

mean something to me, albeit it would obviously be too long for practical

purposes.

But fe80::216:41ff:fee1:b7fd%13 - hmm? sorry but I don't know which

interface 13 might be. It does not "talk" to me.

-- 

Rémi Denis-Courmont

http://www.remlab.net

---

From: Iljitsch van Beijnum <[email-masked]>
Date: Mon, 4 Feb 2008 23:59:55 +0100

On 4 feb 2008, at 22:19, Nathan Ward wrote:

> Shorter term, having a vendor-specific (i.e. manufacturer-, or  
> perhaps ISP-) ULA would be a passable idea.

No, it's a bad idea, because you're about to...

> - What happens when there are two devices of the same model on the  
> link? Does that mean each has to have a unique number in the name?  
> (Apple airport things use part of the MAC address for the initial  
> name, but, this does not need to be typed by the user as is being  
> suggested here..)
> - I'm sure I had more problems in my head a few minutes ago.

...reinvent service discovery.

This all fairly complex to do right but that wheel has been invented  
before, no need to do it again.

BTW those printers I was talking about aren't made by Apple.