Subject: IPv6 MIBs - IPv4-mapped IPv6 addresses

From: [email-masked]
Date: Mon, 3 Jun 2002 09:48:22 -0400

We are planning on implementing an SNMP MIB table that represents packet
trace parameters per interface.  One of the parameters users can specify is
the IP address so that we will only trace packets whose source/destination
IP address match a user specified IP address value.  Due to the fact that
SIIT supports IPv4-mapped IPv6 IP addresses on the wire, we permit users to
trace packets with IPv4-mapped IPv6 addresses for an IPv6 interface.  How
should an IPv4-mapped IPv6 address be represented using the SNMP textual
conventions from RFC3291?  Should the InetAddressType MIB object be set to
unknown(0) or ipv6(2)?  Should the InetAddress MIB object contain a 16-
octet IPv4-mapped IPv6 address?

Also, we are confused about the following explanation in RFC3291:

   The InetAddressIPv4z is intended for use in MIBs (like the TCP-MIB)
   which report addresses in the address family used on the wire, but where
   the entity instrumented obtains such addresses from applications or
   administrators in a form which includes a zone index,
   such as v4-mapped IPv6 addresses.

What is the relationship between a zone index and an IPv4-mapped IPv6
address?  Thanks!

Kristine Adamson
IBM Communications Server for MVS: TCP/IP Development
Internet e-mail:[email-masked]

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From: Bill Fenner <[email-masked]>
Date: Tue, 4 Jun 2002 15:33:45 -0700

I think SIIT communication using v4-mapped addresses should be represented
as InetAddressType ipv6(2), and InetAddress of ::ffff:x.y.z.q .

>What is the relationship between a zone index and an IPv4-mapped IPv6

I think that some implementations provide the zone concept for IPv4
communication, but no sin_scope_id in the sockaddr_in; thus the way to
provide zone info is to use AF_INET6 sockets and IPv4-mapped addresses
to communicate via IPv4 on the wire.  However, since the address family
in the MIB is supposed to reflect the address family on the wire, ipv4z
is required to represent the zone info when performing this trick.

(The zone concept is useful in v4 in some of the same ways as in v6, e.g.
two different zones both using 10.0.1/24)

  Bill
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