IPv4 and IPv6 use the Ethernet II frame format. Some server and desktop OSs 
support changing the frame format to 802.3, although there's no reason to 
do this usually. In the past, some OSs defaulted to 802.3. But most 
implementations these days use Ethernet II.

If a Cisco IOS router receives IP frames encapsulated in an 802.3 header 
from a device, the router sends to that device in 802.3 also. You can't 
configure the Ethernet frame format for IP with Cisco IOS. But you can 
configure the frame format for ARP. Can you think why?

IP isn't the only thing out there, though! :-)

AppleTalk Phase 2 uses IEEE 802.3 with 802.2 and SNAP.

Novell supports four frame types. This is configurable on Cisco IOS routers 
in interface mode with the IPX network command, and it is configurable on 
clients and servers, of course.

NetBEUI uses 802.3 with 802.2.

SNA uses 802.3 with 802.2.

DECnet uses Ethernet II.

IS-IS uses 802.3 with 802.2.

The question of why some books say there are 4 frame formats and some say 2 
frame formats has to do with orientation (Novell orientation versus IP) and 
is really a matter of wording.

The other two frame formats, other than the two you mentioned, are a subset 
of IEEE 802.3 and are as follows:

Novell raw

         Preamble
         Start Frame Delimiter
         Destination Address
         Source Address
         Length
         Data (no 802.2)
         CRC

Preamble
         Start Frame Delimiter
         Destination Address
         Source Address
         Length
         802.2
         SNAP
         Data
         CRC

Hope that helps.

Priscilla

At 12:36 AM 5/29/01, Ken Chipps wrote:
>I am confused about which Ethernet frame type everyone uses with TCP/IP
>today. I understand that there are four different types. I see from the
>Cisco website that they talk about only two of these four. The two they
>discuss are called Ethernet and IEEE 802.3. The one Cisco calls Ethernet has
>the following fields
>
>         Preamble
>         Destination Address
>         Source Address
>         Type
>         Data
>         CRC
>
>The one Cisco calls IEEE 802.3 has
>
>         Preamble
>         Start Frame Delimiter
>         Destination Address
>         Source Address
>         Length
>         Data and 802.2 Header inside the data area as best I can tell
>         CRC
>
>Why do they mention these two only? Who uses what?
>FAQ, list archives, and subscription info: 
>http://www.groupstudy.com/list/cisco.html
>Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]


________________________

Priscilla Oppenheimer
http://www.priscilla.com




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