SNMP over Ethernet
Direct management of devices that have no IP support.
Schoffstall, M., Davin, C., Fedor, M., and J. Case, "SNMP over Ethernet", RFC 1089, DOI 10.17487/RFC1089, February 1989, <https://www.rfc-editor.org/info/rfc1089>.
@misc{rfc1089,
series = {Request for Comments},
number = 1089,
howpublished = {RFC 1089},
publisher = {RFC Editor},
doi = {10.17487/RFC1089},
url = {https://www.rfc-editor.org/info/rfc1089},
author = {M. Schoffstall and C. Davin and M. Fedor and J. Case},
title = {{SNMP over Ethernet}},
pagetotal = 3,
year = 1989,
month = feb,
} RFC text
Contents
Network Working Group M. Schoffstall
Request for Comments: 1089 Rensselaer Polytechnic Institute
C. Davin
MIT Laboratory for Computer Science
M. Fedor
NYSERNet, Inc.
J. Case
University of Tennessee at Knoxville
February 1989
SNMP over Ethernet
Status of This Memo
This memo describes an experimental method by which the Simple
Network Management Protocol (SNMP) as specified in [1] can be used
over Ethernet MAC layer framing [2] instead of the Internet UDP/IP
protocol stack. This specification is useful for LAN based network
elements that support no higher layer protocols beyond the MAC sub-
layer. Distribution of this memo is unlimited.
Overview and Rational
SNMP has been successful in managing Internet capable network
elements which support the protocol stack at least through UDP the
connectionless Internet transport layer protocol. As originally
designed, SNMP is capable of running over any reasonable transport
mechanism (not necessarily a transport protocol) that supports bi-
directional flow and addressability.
Many non-Internet capable network elements are present in local
networks; for example, repeaters and wiring concentrators. They
include both addressability, and programmable intelligence. These
devices are widely used and increasingly important yet, for the most
part, invisible except through proprietary mechanisms.
Specification
Almost all Internet capable network elements use the same mechanism
for encapsulation of the Internet protocol stack regardless of
conformity with the physical characteristics of Ethernet or 802.3,
this mechanism is specified in [3] and [4]. This specification
continues that style with the assignment (by XEROX) of 33100
(hexadecimal 814C) to the Ethernet Type field for SNMP. The data
portion of the Ethernet frame would then be a standard SNMP message
as specified in [1].
References
[1] Case, J., Fedor, M., Schoffstall, M., and J. Davin, "A Simple
Network Management Protocol", RFC-1067, University of
Tennessee at Knoxville, NYSERNet, Inc., Rensselaer Polytechnic
Institute, and Proteon, Inc., August 1988.
[2] DEC, "The Ethernet - A Local Area Network", Version 2.0,
Digital Equipment Corporation, Intel Corporation, Xerox
Corporation.
[3] Hornig, C., "A Standard for the Transmission of IP Datagrams
over Ethernet Networks", RFC-894, Symbolics, April 1984.
[4] Postel, J., and J. Reynolds, "A Standard for the Transmission
of IP Datagrams over IEEE 802 Networks", RFC-1042, USC
Information Sciences Institute, February 1988.
Authors' Addresses
Marty Schoffstall
NYSERNET Inc.
Rensselaer Technology Park
165 Jordan Road
Troy, NY 12180
Phone: (518) 276-2654
EMail: schoff@stonewall.nyser.net
Chuck Davin
MIT Laboratory for Computer Science, NE43-507
545 Technology Square
Cambridge, MA 02139
Phone: (617) 253-6020
EMail: jrd@ptt.lcs.mit.edu
Mark Fedor
Nysernet, Inc.
Rensselaer Technology Park
125 Jordan Road
Troy, NY 12180
(518) 283-8860
Phone: (518) 283-8860
EMail: fedor@patton.NYSER.NET
Jeff Case
University of Tennessee Computing Center
Associate Director
200 Stokely Management Center
Knoxville, TN 37996-0520
Phone: (615) 974-6721
EMail: case@UTKUX1.UTK.EDU
AI ELI5
On this page
§1The Problem
SNMP usually travels inside UDP packets, which sit inside IP packets. But many local area network devices—repeaters, hubs, wiring concentrators—have no software for IP or UDP. They only understand Ethernet MAC-layer frames. Yet these devices have intelligence and can be managed; they are just invisible without a proprietary way to talk to them.
This RFC solves the problem by defining how to wrap SNMP messages directly in Ethernet frames, skipping the whole UDP/IP stack. It is useful for LAN-only devices that support addressability but nothing above the MAC sublayer.
Some machines only understand the simplest kind of message: an Ethernet frame. This shows how to put SNMP inside one.
§2The Ethernet Encapsulation
The specification follows the same style used for IP over Ethernet (RFC 894, RFC 1042). It assigns Ethernet type 0x814C (33100 decimal) to SNMP. A standard SNMP message becomes the data payload of an Ethernet frame with that type field.
No modification to the SNMP message itself is needed. The message is the same as defined in RFC 1067; only the encapsulation changes. Devices on a shared Ethernet segment can address each other directly because Ethernet provides both addressability and bidirectional flow.
An Ethernet frame carries data with a type number. SNMP over Ethernet uses type 0x814C to say 'the data inside is an SNMP message.'
§3Scope and Status
This approach is experimental and meant for local area networks where devices have no higher-layer protocol support. It does not modify SNMP itself, only the transport. The technique applies to any network element that can address other elements on the MAC layer and has programmable intelligence, such as bridges and managed switches.
This is an experimental way to manage local-only devices. It works because Ethernet already lets devices find and talk to each other.