Subject: May one configure IID= "0" for an address ?

From: [email-masked]
Date: Wed, 30 Apr 2003 14:14:47 +0200

Hi,
I have found nowhere in (draft)-RFCs a restriction on the value
an Interface ID can take. So in principle any values in [0, 2**64-1] could
be configured as IID for an IPv6 address.

However, RFC 3513, section 2.6.1 defines the "Subnet-Router Anycast
address" as being <subnet prefix>::

Does that mean that configuring  IID = 0 might interfere or conflict with
some anycast mechanism ? and consequently that configuring IID=0
for an address should be avoided ? ...or what do I miss there ?

Thanks,
Kind regards,
Robert

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From: Bob Hinden <[email-masked]>
Date: Wed, 30 Apr 2003 10:27:56 -0700

Robert,

>be configured as IID for an IPv6 address.

Zero is a legitimate address for any field in an IPv6 address.

>address" as being <subnet prefix>::

As you noted that RFC3513 (and it's predecessors) defines the 
"subnet=router anycast address" as any prefix with the remaining bits of 
the address set to zero.

>for an address should be avoided ? ...or what do I miss there ?

Using a IID of zero does conflict with the subnet anycast address.  So zero 
IID's are legal, but are reserved for the "subnet=router anycast address".

Does that help?

Bob