Okay, I have a guess...a total W.A.G., and I wasn't able to back it up with some quick
research, but here it is:
The answer to this has something to do with ARP packets. My guess is that they assume
the presence of Ethernet_II frames when constructing ARP packets and these would be
inoperable if some other ethernet frame were being used.
That would explain why the default *had* to be Ethernet_II. If ARP breaks, IP over
ethernet breaks.
Am I right?? I'm going to keep digging to see if I can find some more details about
this. I may be chasing down the wrong street. Let me know if I'm even close! :-)
John
>
> OK, Leigh Anne, you're just going to have to come out and tell us what you
> are getting at. The suspense is killing me. &;-)
>
> The only time I've ever configured an Ethernet encapsulation, it has been
> part of the ipx network command. As we know, Novell mucked things up and
> supports four frame types, so being able to configure the frame type is
> necessary for IPX. A unique feature of IPX is that you can configure
> multiple networks on a single segment. Each of them must have a different
> encapsulation. In fact that is how you support networks with devices
> configured for different encapsulations.
>
> I don't even know that you can configure the encapsulation for IP on
> Ethernet on a router. Can you? Or is that what you're getting at. IP
> doesn't care.
>
> With IP, 99% of the world uses Ethernet V2 (dest, src, EtherType). I just
> tried to change it on my PC and I couldn't, although I think I have seen
> that capability on other PCs. But my guess is that if I did change it, the
> router could still handle it.
>
> Priscilla
>
> At 12:33 PM 2/7/01, Tony van Ree wrote:
> >Hi,
> >
> >I understood it to tell me that there is a common method used by a number
> >of manufacturers and protocols. Some other companies and protocols had
> >made some changes. The default was used as it was the most
> >common. Ethernet_II had been around for quite a while before the 802.3
> >and almost all devices manufacturers ethernet cards and the like could
> >handle Ethernet_II but not necessarily 802.3.
> >
> >Maybe I mis understood.
> >
> >Teunis
> >
> >
> >On Tuesday, February 06, 2001 at 05:36:32 PM, [EMAIL PROTECTED] wrote:
> >
> > > I did read Priscilla's post. She addressed the issue of WHY Ethernet_II is
> > > the default frame type selected for IP, but didn't examine why IP
> > requires a
> > > default frame type in the first place. IPX uses a default frame type
> > > because different Ethernet encapsulations are not able to co-exist
> > within an
> > > IPX network -- however different Ethernet encapsulations (Ethernet_II and
> > > Ethernet 802.3) ARE able to co-exist within an IP network. As such,
> > what is
> > > the importance of a default Ethernet encapsulation for IP?
> > >
> > > That's what I've been challenging John to think about. Once he understands
> > > where the default Ethernet encapsulation comes into play, he could answer
> > > his question as to whether there "would there be a good reason to change to
> > > a
> > > different frame type, or would we only benefit from a different frame type
> > > in a non-IP environment or mixed environment".
> > >
> > >
> > >
> > >
> > > -----Original Message-----
> > > From: Tony van Ree [mailto:[EMAIL PROTECTED]]
> > > Sent: February 6, 2001 5:06 PM
> > > To: [EMAIL PROTECTED]; John Neiberger; [EMAIL PROTECTED]
> > > Subject: RE: Another 802.3 and Ethernet Question
> > >
> > >
> > > Hi,
> > >
> > > I'm sorry I did not cover the rest of the ethernat frame types. This was
> > > covered earlier this week. Priscilla covered it really well in one of her
> > > replys on a similar question.
> > >
> > > Teunis
> > >
> > >
> > > On Tuesday, February 06, 2001 at 04:55:01 PM, [EMAIL PROTECTED] wrote:
> > >
> > > > Yes, with respect to IPX, that's correct--and that answers my first
> > > > question.
> > > >
> > > > My second question asked about what was the purpose of a default Ethernet
> > > > frame type for use with IP. Using IPX as an analogy, does a router only
> > > > route Ethernet_II frames if no Ethernet frame type has been specified?
> > > Does
> > > > a router drop IEEE 802.3 frames by default? To route IEEE 802.3 frames,
> > > is
> > > > any additional configuration required?
> > > >
> > > > And with that, we're lead back to John's original question: What is the
> > > > purpose of a default Ethernet frame type for IP?
> > > >
> > > > -----Original Message-----
> > > > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of
> > > > Tony van Ree
> > > > Sent: February 6, 2001 2:51 PM
> > > > To: Leigh Anne Chisholm; John Neiberger; [EMAIL PROTECTED]
> > > > Cc: Priscilla Oppenheimer
> > > > Subject: RE: Another 802.3 and Ethernet Question
> > > >
> > > >
> > > > Hi,
> > > >
> > > > Those not specified by the router are either routed by the server or
> > > produce
> > > > IPX protol errors and are dropped.
> > > >
> > > > It is important not to have the various frame types set on the servers or
> > > > service advertisers. If for example you are normally using Novell-Ether
> > > > (802.3) and you put in a server using Netware 4.x running SAP (802.2).
> > > Now
> > > > when you put in the first server you configure both the SAP and Novell
> > > Ether
> > > > in the server. You have 802.3 (Novell-ether) configured in the router.
> > > > Pull out the original server and you have no network. Othen you will lose
> > > > half of your local clients.
> > > >
> > > > Have lose networks and or frame types can also create some horrible
> > little
> > > > routing loops and unwanted traffic. SAP's, RIP updates etc.
> > > >
> > > > Let the router route and servers serve.
> > > >
> > > > Another one that sometimes grabs you.
> > > >
> > > > Teunis,
> > > > Hobart, Tasmania
> > > > Australia
> > >
> > >
> > >
> >
> >
> >--
> >www.tasmail.com
> >
> >
> >_________________________________
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>
>
> ________________________
>
> Priscilla Oppenheimer
> http://www.priscilla.com
>
> _________________________________
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> Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
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