identifier
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... DHCPv4 client implementations that conform to this specification use
a DHCP Unique Identifier (DUID) as specified in Dynamic Host
Configuration Protocol for IPv6 (DHCPv6 ...
... addresses
certain limitations in the functioning of RFC 2131draft/2132-style DHCP
client identifiers.
This document first describes the problem to be solved. It then
...
...
RFC 2132draft recommends that client identifiers be generated by using the
permanent link-layer address of the network interface ...
... client loses its IP address
and any other resources associated with its old identifier (for
example, its domain name as published through the DHCPv4 server ...
... when a boot monitor such as a Pre-Boot Execution Environment (PXE)
loader specifies one DHCP client identifier, and then the operating
system loaded by the boot loader specifies a different identity.
...
... DHCPv4 clients and servers
to identify clients. In some cases, the value of the 'client
identifier' option is used to mediate access to resources (for
example, the client's domain name ...
... 3315prop specify different methods for
deriving client identifiers. These methods guarantee that the DHCPv4
...
... DHCPv4
and DHCPv6 identifiers will be different. This means that mediation
of access to resources using these identifiers will not work
...
... DHCPv6 identifiers will be different. This means that mediation
of access to resources using these identifiers will not work
correctly in cases where a node may be configured using DHCPv4 ...
... RFC 2131draft does not require the use of a client identifier. ...
... DHCPv4 server to identify clients either by using
the client identifier option sent by the client or, if the client did
...
... not send one, the client's link-layer address. Like the client
identifier format recommended by RFC 2131draft, this suffers from the
problems previously described in sections 4.2 and 4.3.
...
...
In order to address the problems stated in section 4, DHCPv4 client
identifiers must have the following characteristics:
- They must be persistent, in the sense that a particular host ...
... - They must be persistent, in the sense that a particular host's
client identifier must not change simply because a piece of network
hardware ...
... same IP
address. In such cases, it must be possible for the client to use
exactly the same identifier for each interface.
...
... - DHCPv4 servers that do not conform to this specification, but that
are compliant with the older client identifier specification, must
correctly handle client identifiers sent by clients ...
... are compliant with the older client identifier specification, must
correctly handle client identifiers sent by clients that conform to
this specification.
...
... DHCPv4 clients of the chaddr field of the DHCPv4 packet
as an identifier must be deprecated.
- DHCPv4 client identifiers ...
... identifier must be deprecated.
- DHCPv4 client identifiers used by dual-stack hosts that also use
...
... requirements, we need
to construct a DHCPv4 client identifier out of two parts. One part
must be unique to the host on which the client ...
... identity being presented. The DHCP
Unique Identifier (DUID) and Identity Association Identifier ...
... Unique Identifier (DUID) and Identity Association Identifier (IAID)
specified in RFC 3315prop satisfy these requirements ...
... DHCPv4 clients conforming to this specification MUST use stable
DHCPv4 node identifiers in the dhcp-client-identifier option. DHCPv4
clients ...
... DHCPv4 node identifiers in the dhcp-client-identifier option. DHCPv4
clients MUST NOT use client identifiers based solely on layer ...
... client-identifier option. DHCPv4
clients MUST NOT use client identifiers based solely on layer two
addresses ...
... section 9.2 of RFC 3315prop. DHCPv4 clients MUST send a 'client
identifier' option containing an Identity Association Unique
Identifier ...
... client
identifier' option containing an Identity Association Unique
Identifier, as defined in section 10 of RFC 3315prop, and a DHCP Unique
Identifier ...
... Unique
Identifier, as defined in section 10 of RFC 3315prop, and a DHCP Unique
Identifier, as defined in section 9 of RFC 3315prop. These together
constitute an RFC 3315prop ...
... The general format of the DHCPv4 'client identifier' option is
defined in section 9.14 of RFC 2132draft.
...
... To send an RFC 3315prop-style binding identifier in a DHCPv4 'client
identifier' option, the type of the 'client identifier ...
... binding identifier in a DHCPv4 'client
identifier' option, the type of the 'client identifier' option is set
to 255. The type field ...
... identifier in a DHCPv4 'client
identifier' option, the type of the 'client identifier' option is set
to 255. The type field is immediately followed by the IAID, which is
...
... opaque 32-bit quantity. The IAID is immediately followed by the
DUID, which consumes the remaining contents of the 'client
identifier' option. The format of the 'client identifier' option is
as follows:
...
... 32-bit quantity. The IAID is immediately followed by the
DUID, which consumes the remaining contents of the 'client
identifier' option. The format of the 'client identifier' option is
as follows:
...
... 2131draft and RFC 2132draft, in the sense
that they ignore the 'client identifier' option and use the client's
hardware address ...
... DHCPv4 servers that conform to this specification MUST use the
'client identifier' option to identify the client if the client sends
...
... client, even if the client sends
a client identifier option. This is ONLY permitted in the case where
the DHCPv4 server administrator ...
... In section 2 of RFC 2131draft, on page 9, the text that reads "; for
example, the 'client identifier' may contain a hardware address,
identical to the contents of the 'chaddr' field, or it may contain
...
... hardware address,
identical to the contents of the 'chaddr' field, or it may contain
another type of identifier, such as a DNS name" is deleted.
...
... 2131draft, the text "The client MAY choose to
explicitly provide the identifier through the 'client identifier'
option. If the client ...
... client MAY choose to
explicitly provide the identifier through the 'client identifier'
option. If the client supplies a 'client identifier ...
... client identifier'
option. If the client supplies a 'client identifier', the client
MUST use the same 'client identifier ...
... client identifier', the client
MUST use the same 'client identifier' in all subsequent messages, and
the server MUST use that identifier to identify the client ...
... MUST use the same 'client identifier' in all subsequent messages, and
the server MUST use that identifier to identify the client. If the
client ...
... client. If the
client does not provide a 'client identifier' option, the server MUST
use the contents of the 'chaddr' field to identify the client." is
...
... client." is
replaced by the text "The client MUST explicitly provide a client
identifier through the 'client identifier' option. The client MUST
...
... replaced by the text "The client MUST explicitly provide a client
identifier through the 'client identifier' option. The client MUST
use the same 'client identifier ...
... client identifier' option. The client MUST
use the same 'client identifier' option for all messages."
In the same section, the text "Use of 'chaddr' as the client ...
...
In the same section, the text "Use of 'chaddr' as the client's unique
identifier may cause unexpected results, as that identifier may be
associated with a hardware ...
... In the same section, the text "Use of 'chaddr' as the client's unique
identifier may cause unexpected results, as that identifier may be
associated with a hardware interface ...
... new
client. Some sites may choose to use a manufacturer's serial number
as the 'client identifier', to avoid unexpected changes in a client's
network ...
... interfaces among
computers. Sites may also choose to use a DNS name as the 'client
identifier', causing address leases to be associated with the DNS
name rather than a specific hardware ...
... 2131draft, the text "The client MAY include a
different unique identifier" is replaced with "The client MUST
include a unique identifier ...
... unique identifier" is replaced with "The client MUST
include a unique identifier".
In section 3.1, items 4 and 6; section 3.2 item 3 and 4; and section
...
... 4.3.1, where RFC 2131draft says that 'chaddr' may be used instead of the
'client identifier' option, the text "or 'chaddr'" and "'chaddr' or"
is deleted.
...
... Note that these changes do not relieve the DHCPv4 server of the
obligation to use 'chaddr' as an identifier if the client does not
send a 'client identifier ...
... identifier if the client does not
send a 'client identifier' option. Rather, they oblige clients that
conform with this document to send a 'client identifier ...
... client identifier' option. Rather, they oblige clients that
conform with this document to send a 'client identifier' option, and
not rely on 'chaddr' for identification. DHCPv4 servers MUST use
...
... not rely on 'chaddr' for identification. DHCPv4 servers MUST use
'chaddr' as an identifier in cases where 'client identifier' is not
sent, in order to support old clients ...
... DHCPv4 servers MUST use
'chaddr' as an identifier in cases where 'client identifier' is not
sent, in order to support old clients that do not conform with this
...
...
The text in section 9.14, beginning with "The client identifier MAY
consist of" through "that meet this requirement for uniqueness." is
...
... consist of" through "that meet this requirement for uniqueness." is
replaced with "the client identifier consists of a type field whose
value is normally 255, followed by a four-byte IA_ID field, followed
...
... over the network. In such cases, it may be that the first-stage boot
uses a different client identifier, or no client identifier, than the
subsequent stage or stages.
...
... network. In such cases, it may be that the first-stage boot
uses a different client identifier, or no client identifier, than the
subsequent stage or stages.
...
... Some DHCP servers work around this problem for the common case where
the boot Programmable Read Only Memory (PROM) presents no client
identifier, and the operating system DHCP client presents a client
identifier ...
... client
identifier, and the operating system DHCP client presents a client
identifier constructed from the Message Authentication Code (MAC)
...
... address of the network interface -- both are treated as the same
identifier. This prevents the consumption of an extra IP address.
...
...
A compliant DHCPv4 client does not use a client identifier
constructed from the MAC address of the network interface ...
... detect whether it is running on legacy hardware; if it is, it uses
the old identifier; if it is not, it follows the scheme described in
the previous paragraph.
...