



Network Working Group                                        D. Eastlake
Internet-Draft                                               Independent
Intended status: Standards Track                            11 June 2025
Expires: 13 December 2025


      MAC Address for Layer 3 Link Local Discovery Protocol (LLDP)
                       draft-eastlake-lldp-mac-04

Abstract

   IEEE 802 has defined a number of protocols which can operate between
   adjacent Ethernet stations at Layer 2, including bridges, and may be
   useful between Layer 3 aware stations such as IP routers and hosts.
   An example is the Link Layer Discover Protocol (IEEE Std 802.1AB,
   LLDP).  This document specifies a MAC address that can be used for
   this purpose for interoperability despite intervening bridges.

Status of This Memo

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   provisions of BCP 78 and BCP 79.

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   This Internet-Draft will expire on 13 December 2025.

Copyright Notice

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   document authors.  All rights reserved.

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   provided without warranty as described in the Revised BSD License.



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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Notations Used in This Document . . . . . . . . . . . . .   2
   2.  Network Layers and MAC Addresses  . . . . . . . . . . . . . .   3
   3.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   5
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   5.  Normative References  . . . . . . . . . . . . . . . . . . . .   5
   6.  Informative References  . . . . . . . . . . . . . . . . . . .   5
   Appendix A.  EUI-48 Assignment Request  . . . . . . . . . . . . .   6
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   7

1.  Introduction

   IEEE 802 [IEEE802] has defined a number of protocols which operate
   between adjacent Ethernet stations at Layer 2, including bridges,
   such as the Link Layer Discover Protocol ([IEEE802.1AB] LLDP) and the
   Link Aggregation Control Protocol ([IEEE802.1AX] LACP).  LLDP and
   other such protocols may be useful between adjacent Layer 3 [ISO]
   aware stations such as IP routers and hosts.  This document specifies
   a MAC address that can be used for that purpose despite intervening
   bridges.

1.1.  Notations Used in This Document

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in BCP
   14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

   In this document the terms/acronyms listed below have the indicated
   meaning:

   "LACP"  Link Aggregation Control Protocol [IEEE802.1AX].

   "Layer 2"  Layer 2 in the ISO model [ISO].

   "Layer 3"  Layer 3 in the ISO model [ISO].

   "LLDP"  Link Layer Discovery Protocol [IEEE802.1AB].

   "MAC"  Media Access Control [RFC9542] (not Message Authentication
      Code).

   "PDU"  Protocol Data Unit.





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2.  Network Layers and MAC Addresses

   LLDP [IEEE802.1AB] is a Layer 2 [ISO] protocol providing for the
   unacknowledged announcement of information by an Ethernet station to
   other stations on the same Ethernet link.  There are proposals for
   the use of LLDP between L3 aware stations such as between a host and
   its first hop IP router or between IP adjacent routers.  Examples are
   [LLDP1] [LLDP2] [LLDP3].

   As illustrated in the figure below, uses of LLDP and similar
   protocols between Ethernet stations have a scope of adjacency
   controlled by the multicast destination MAC address [RFC9542] of the
   Ethernet frame used to transmit the LLDP PDU.

   *  Customer bridges use 0x0180C2000000 for LLDP and the like.  Frames
      sent to that address are transparently forwarded through any lower
      level bridges, such as the provider bridges shown below.  On the
      other hand, IP routers do not forward frames sent to unknown
      multicast addresses unless configured to do so.  Thus, frames sent
      to this address by the customer bridge shown near the bottom of
      the figure will not reach either of the customer bridges shown
      higher up in the figure due to the intervening IP router.

   *  Provider bridges use 0x0180C2000008 for LLDP.  Frames sent to that
      address are transparently forwarded by lower level bridges (not
      shown in the figure) and are blocked by higher level bridges, such
      as customer bridges.  They are also blocked as described in the
      previous point by IP routers.

   LLDP or similar Ethernet frames intended to be between adjacent IP
   routers or between a host and its first hop IP router need to avoid
   use of a destination MAC address that might be intercepted by any
   intervening bridge.  The multicast destination MAC addresses used by
   bridges are the block from 0x0180C2000000 to 0x0180C200003F but it
   would be best to be conservative and avoid all addresses from
   0x0180C2000000 to 0x0180C2FFFFFF.  An address meeting this criterion
   is specified in Section 3 below and its use is RECOMMENDED.














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               +-------+
               |  Host |
               +-------+
                   |
              +---------+
              |L3 Router|
              +---------+
                   .     \
                   .      +---------------+
                   .      |Customer Bridge|
                   .      +---------------+
                   .              :        \
                   .              :         +---------------+
                   .              :         |Provider Bridge|
                   .              :         +---------------+
                   .              :                |
                   .              :         +---------------+
                   .              :         |Provider Bridge|
                   .              :         +---------------+
                   .              :        /
                   .      +---------------+
                   .      |Customer Bridge|
                   .      +---------------+
                   .     /
              +---------+
              |L3 Router|
              +---------+
                   .     \
                   .      +---------------+
                   .      |Customer Bridge|
                   .      +---------------+
                   .     /
               +-------+
               |  Host |
               +-------+

                          Figure 1: Geneve Header

      Note: The above figure is simplified.  For example, where one or
      two customer bridges or provider bridges are shown, there could be
      zero or some larger number.  There could also be one or more
      bridges between the host shown at the top of the figure and its
      first hop IP router.  Only two levels of bridge are shown
      (customer and provider) but [IEEE802.1Q] specifies additional
      levels of bridges.






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3.  IANA Considerations

   IANA is requested to assign a 48-bit multicast MAC address
   [0x00000E900004 suggested] under the IANA OUI for use with Link Layer
   Discovery Protocol and similar protocols between Layer 3 routers as
   per the request in Appendix A.  The entry in the "IANA Multicast
   48-bit MAC Addresses" registry is as follows:

            Addresses   Usage                      Reference
           ---------  -------------------------  ---------------
            [tbd]     Layer 3 LLDP and the like  [this document]

   (Alternatively, there could be more than on MAC address assigned for
   different L3 or higher layer [ISO] purposes.)

4.  Security Considerations

   TBD

5.  Normative References

   [IEEE802.1AB]
              802, IEEE., "IEEE Standard for Local and metropolitan area
              networks - Station and Media Access Control Connectivity
              Discovery", IEEE Std 802.1AB-2016, 29 January 2016.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

   [RFC9542]  Eastlake 3rd, D., Abley, J., and Y. Li, "IANA
              Considerations and IETF Protocol and Documentation Usage
              for IEEE 802 Parameters", BCP 141, RFC 9542,
              DOI 10.17487/RFC9542, April 2024,
              <https://www.rfc-editor.org/info/rfc9542>.

6.  Informative References

   [IEEE802.1AX]
              802, IEEE., "IEEE Standard for Local and metropolitan area
              networks - Link Aggregation", IEEE Std 802.1AX-2014.





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   [IEEE802.1Q]
              802.1 WG, IEEE., "Bridges and Bridged Networks", IEEE Std 
              802.1Q-2014, 3 November 2014.

   [IEEE802]  802, IEEE., "IEEE 802 LAN/MAN Standards Committee", IEEE
              Std 802, <http://www.ieee802.org>.

   [ISO]      ISO/IEC, "Information technology - Open Systems
              Interconnection - Basic Reference Model: The Basic Model",
              ISO/IEC 7498-1:1994(E), 15 June 1996.

   [LLDP1]    Lindem, A., Patel, K., Zandi, S., Haas, J., and X. Xu,
              "BGP Logical Link Discovery Protocol (LLDP) Peer
              Discovery", Work in progress,
              <https://datatracker.ietf.org/doc/draft-acee-idr-lldp-
              peer-discovery/>.

   [LLDP2]    Congdon, P. and P. Bottorff, "LSVR IETF Organizationally
              Specific TLVs for IEEE Std 802.1AB (LLDP)", work
              in progress, <https://datatracker.ietf.org/doc/draft-
              congdon-lsvr-lldp-tlvs/>.

   [LLDP3]    Richardson, M. and L. Xia, "Autonomic Control Plane design
              for Layer-Two Switched Networks", Work in progress,
              <https://datatracker.ietf.org/doc/draft-richardson-anima-
              l2-friendly-acp/>.

Appendix A.  EUI-48 Assignment Request

   (not yet submitted)

   Applicant Name: Donald E.  Eastlake III

   Applicant Email: d3e3e3@gmail.com

   Applicant Telephone: +1-508-333-2270

   Use Name: L3-LLDP

   Document: [this document]

   Specify whether this is an application for EUI-48 or EUI-64
   identifiers: EUI-48

   Size of Block requested: 1

   Specify multicast, unicast, or both: multicast




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Author's Address

   Donald E. Eastlake 3rd
   Independent
   2386 Panoramic Circle
   Apopka, Florida 32703
   United States of America
   Phone: +1-508-333-2270
   Email: d3e3e3@gmail.com










































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