| Internet-Draft | L3 LLDP MAC Address | December 2024 |
| Eastlake | Expires 11 June 2025 | [Page] |
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.¶
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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.¶
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:¶
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.¶
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.¶
+-------+
| Host |
+-------+
|
+---------+
|L3 Router|
+---------+
. \
. +---------------+
. |Customer Bridge|
. +---------------+
. : \
. : +---------------+
. : |Provider Bridge|
. : +---------------+
. : |
. : +---------------+
. : |Provider Bridge|
. : +---------------+
. : /
. +---------------+
. |Customer Bridge|
. +---------------+
. /
+---------+
|L3 Router|
+---------+
. \
. +---------------+
. |Customer Bridge|
. +---------------+
. /
+-------+
| Host |
+-------+
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.¶
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.)¶
TBD¶
(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¶