Subject: Re: DAD vs. DIID - multiple IIDs?

From: Markku Savela <[email-masked]>
Date: Mon, 29 Jul 2002 20:31:03 +0300

> From: "Deshpande, Prasad" <[email-masked]>

> I have some questions related to multiple IIDs on an interface
> 
> - When and why would someone configure multiple IIDs on an interface?

offhand, perpaps

- for a server you might want manually configure nice "prefix::1"
  address in addition to the automaticly generated id (or even many
  id's you have webserver: id=1, mailserver: id=2, etc.). Now,
  depening on needs, you can designate any host as server by adding
  the servers "locally-well-known-id" to a host (and removing it from
  another).

- privacy draft (3041?) didn't exactly call for generation of id only,
  but it could be done that way too (just generate random id's to be
  used).

> - If multiple IIDs are configured on an interface, does that imply that 
>   the interface has multiple link-local addresses, one created from each 
>   IID.

In my case, yes.

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From: "Deshpande, Prasad" <[email-masked]>
Date: Mon, 29 Jul 2002 13:05:49 -0400

> -----Original Message-----
> From: Markku Savela [mailto:[email-masked]]
> Sent: Monday, July 29, 2002 6:34 AM
> To: [email-masked]
> Cc: [email-masked]; [email-masked]
> Subject: Re: DAD vs. DIID
> 
>  - I've 3 prefixes and 3 ids, thus I have total of 9 addresses DADded.
> 
>  - I receive 4th prefix, => I do a DAD for 3 new addresses. Do I do
>    them in parallel or do I have to do them one after another? 
> 
>  - I configure a new additional ID => I do a DAD for 4 new 
> addresses. Do I do
>    them in parallel or do I have to do them one after another? 
> 
> Apparently, KAME is not able to configure multiple plain IDs to be
> combined freely with all announced prefixes? Or can it?

- If multiple IIDs are configured on an interface, does that imply that 
  the interface has multiple link-local addresses, one created from each 
  IID. I didn't see any RPC/draft which prevents one from having multiple 
  link-local addresses. On the other hand I couldn't find any statement 
  that says that there must be a link local address for each IID.

thanks
-prasad

---

From: Robert Elz <[email-masked]>
Date: Tue, 30 Jul 2002 13:58:11 +0700

Date:        Mon, 29 Jul 2002 13:05:49 -0400
    From:        "Deshpande, Prasad" <[email-masked]>
    Message-ID:  <[email-masked]>

  | - When and why would someone configure multiple IIDs on an interface?

One obvious place would be for various kinds of "hot standby" protocols,
when one node needs to take over the functionality of another when the
other dies.   There the node will have its own addresses (and IIDs) but
will also want those of the node it is pretending to be.

  | - If multiple IIDs are configured on an interface, does that imply that 
  |   the interface has multiple link-local addresses, one created from each 
  |   IID. I didn't see any RPC/draft which prevents one from having multiple 
  |   link-local addresses. On the other hand I couldn't find any statement 
  |   that says that there must be a link local address for each IID.

That's because there is no rule either way.   There's nothing preventing a
node (at least attempting to) configure a LL addr with the same IID as that
used for every global addr it configures.   But nor is there any requirement
that it do that.   Nodes are required to have a LL addr on every link.
Beyond that, almost anything is possible (requiring a LL addr with an IID
before allowing a global addr using the same IID will defeat some entirely
reasonable configurations, but that just makes that particular implementation
less functional than others, not incorrect).

kre