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Today I was reading through some documentation about the fundamentals of networks (IP, Ethernet, MPLS, ...). And while looking at the Ethernet Types that can be used in the Ethernet Frame I saw there was an Ethertype for Simple Network Management Protocol (SNMP)(0x814C). But as I could remember, SNMP is an application protocol running over UDP. So why is there an EtherType for?

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Because there was networks that used protocols other then TCP/IP. See Netware for example. –  Zoredache Dec 14 '12 at 16:46
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Here you go: ietf.org/rfc/rfc1089.txt –  joeqwerty Dec 14 '12 at 17:08
    
@joeqwerty Put that in an answer, if you would. I was to do that, but you beat me to it . Fair is fair: You were first. –  Tonny Dec 14 '12 at 18:55
    
@Zoredache Netware and the others over which you can do SNMP (like DecNET, NetBEUI, NetBios) are still L3 protocols, like TCPIP and so just use the ethertype as would be expected for that L3 protocol. Joeqwery got it right. SNMP can be run directly over ethernet, in which case it is a L2 protocol, which requires an ethertype. –  Tonny Dec 14 '12 at 18:59
    
@Tonny agreed, I was just trying to point out that there was networks before TCP/IP was common. I suspect there are many people now, who have never even used a L3 protocol other then TCP/IP. –  Zoredache Dec 14 '12 at 19:10

2 Answers 2

up vote 3 down vote accepted

The SNMP EtherType (SNMP over Ethernet) is meant for devices that don't have support above Layer 2 of the OSI Model. For more information have a read of RFC 1089:

http://www.ietf.org/rfc/rfc1089.txt

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Upvoted as promised. –  Tonny Dec 14 '12 at 19:00
    
@Tonny - Thx... –  joeqwerty Dec 14 '12 at 19:01

SNMP can run over TCP as well.

There is a nice comparison of using SNMP over both protocols here: http://stackoverflow.com/questions/3565975/why-is-snmp-usually-run-over-udp-and-not-tcp-ip

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Wrong. Has nothing to do with it. See my comment above. –  Tonny Dec 14 '12 at 19:00
    
@Tonny, well..should admit I've posted this answer without much research. Should it be deleted? –  Pavel A Dec 15 '12 at 8:57
    
I would keep it in, if just for the link you provided, which is interesting in it's own right. –  Tonny Dec 15 '12 at 10:20

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