Subject: Several Interface IDs on a given IPv6 Interface ?

From: [email-masked]
Date: Thu, 16 May 2002 13:25:22 +0200

Hello all,
Could anyone advice on the following ?

On a given IPv6 Interface on a router, I understand that it is allowed
to configure a global unicast address with an Interface_ID
which is *different* from the Interface_ID of the Link Local Address.

- is this something that should be discouraged
or instead
- can this be considered as normal practice e.g. for operator
convenience ?

Thanks,
- Robert

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From: Pekka Savola <[email-masked]>
Date: Thu, 16 May 2002 15:50:16 +0300 (EEST)

> - can this be considered as normal practice e.g. for operator

We do the latter.  On the other hand, using the same IID is less manual 
configuring, but (probably) more documenting or remembering.  It's the 
user's choice.

I see nothing worth discouraging here.

The only thing (from specification point-of-view) here is that if IID is 
the same, you don't need to perform DAD for global address if you 
performed it for the link-local address.

-- 
Pekka Savola                 "Tell me of difficulties surmounted,
Netcore Oy                   not those you stumble over and fall"
Systems. Networks. Security.  -- Robert Jordan: A Crown of Swords

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From: Francis Dupont <[email-masked]>
Date: Thu, 16 May 2002 20:39:21 +0200

In your previous mail you wrote:

   
=> IMHO the second and if the software complains it should give a way
to setup the interface ID before to create the link-local address.

Regards

[email-masked]

PS: I deeply dislike the uncontrolled autoconfiguration of a link-local
address to every interfaces a la KAME.
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From: Sebastien Roy <[email-masked]>
Date: Thu, 16 May 2002 14:52:25 -0400

> - can this be considered as normal practice e.g. for operator

One could also envision using multiple interface IDs on a single
interface to (auto)configure multiple addresses on that interface
using a single prefix.  For example, a host receives a single global
prefix from its router and configures multiple global addresses using
that single prefix.

-Sebastien

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From: Jun-ichiro itojun Hagino <[email-masked]>
Date: Fri, 17 May 2002 04:56:03 +0900

>> - can this be considered as normal practice e.g. for operator

	it is perfectly legal to have gobal unicast address with different
	interface ID.  i usually assign the following to servers:
	A) autoconfigured global unicast address
	B) manually configured global unicast address, which will not change
	   even if we change ethernet cards.
	i would register (B) to DNS forward mapping.  sometimes I register
	(A) too.

itojun

rtk0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 1500
	address: 08:00:74:50:44:1e
	media: Ethernet autoselect (none)
	status: active
	inet6 fe80::a00:74ff:fe50:441e%rtk0 prefixlen 64 scopeid 0x1
	inet6 3ffe:501:ffff:ffff:a00:74ff:fe50:441e prefixlen 64	<-- A
	inet6 3ffe:501:ffff:ffff::cafe prefixlen 64			<-- B
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