Hmm....<pondering>....
My first supposition is that they decided to default to the oldest frame
type for interoperability. A few years ago, there were probably more
network devices that used only the Ethernet_II frame type. As technology
progressed, vendors added new frame types to their devices, with the
Ethernet_II frame type remaining the common denominator.
If a particular network had a mix of older and newer ethernet devices, the
older ones might only understand the Ethernet_II frame type, and we wouldn't
want to confuse them.
If that were the case, it would make sense to use the older frame type as
the default, but manually switch to some other frame type if it were
advantageous to do so.
Hmm.....<more pondering>...
I just checked the NIC on my PC here at work where we use Netware, so we
have IPX running. In the IP settings, there is no option for different
frame types. However, in the IPX settings, I can pick any of the four
possible frame types. This is something else that had never really occurred
to me: Why can't I pick a different frame type for IP use? Doesn't IP work
using the IEEE 802.3 frame type? I thought that it would.
I need to do some more research. I just checked, and the Caslow book
doesn't even go into that much detail on Ethernet. I guess I'll be doing
even more surfing when I should be working! <g>
I'm getting the feeling that at some point today a light bulb is going to go
off inside my head and I'll have a different outlook on my understanding of
all-things-ethernet.
John
> To answer your question, my question to you John, would be this:
>
> What is the purpose of the default Ethernet frame type on a Cisco router?
>
> You've posed an excellent question - one that I mulled over for quite
some
> time until I answered the question I've asked you to solve...
Understanding
> why things work the way they do is the best way to understand and
> troubleshoot networks.
>
>
> -- Leigh Anne
>
> -----Original Message-----
> From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of
> John Neiberger
> Sent: February 5, 2001 8:38 AM
> To: [EMAIL PROTECTED]
> Subject: Another 802.3 and Ethernet Question
>
>
> While studying for CIT, I noticed something that had never occurred to me
> before. The default ethernet frame type on a Cisco router is
Ethernet_II,
> but the only physical interface specified by Ethernet version 2 is 50-ohm
> coax, IIRC, similar to 10base5 On 10baseT or 100baseTX interfaces, which
> are on every router I've ever worked with, why is the default frame type
not
> IEEE 802.3?
>
> Ethernet_II only has a type field, while IEEE 802.3 frames include 802.2
> information. What sorts of functionality would be available through the
use
> of that frame type that are not available with Ethernet_II?
>
> In IP-only environments, 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?
>
> Thanks,
> John
>
>
>
>
>
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