RE: Another 802.3 and Ethernet Question
I am also confused about the question itself.
The basic default behavior of Cisco routers is to try to identify the
protocol type of a frame, and send it either to the bridging code or
the router code for that protocol on that interface. If the
protocol type is not supported, drop the frame.
I don't know this, but I can reasonably assume that IP protocol
identification is hard-coded for the Ethernet II IP Ethertype and for
802.2 IP. IP might be treated as a special case, of which the router
is agnostic about encapsulation Still, the encapsulation should be
meaningful if and only if appropriate routing or bridging is enabled
for the interface.
ARP has a protocol type field so that wouldn't seem like the reason.
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
RE: Another 802.3 and Ethernet Question
What about when the router itself is generating the ARP? I need to find more details about how the ARP packet is constructed. I see a little bit about it in my CIT study guide, but I'd like more details, specifically about the protocol field and its options. If there were no default encapsulation type, I'm thinking that the router would not be able to construct ARP packets. But then we would all just have to learn to add something like "encapsulation arpa" to our ethernet configs. I still don't really see why there *has* to be a default, except that it might lessen the configuration burden on us. I am also confused about the question itself. The basic default behavior of Cisco routers is to try to identify the protocol type of a frame, and send it either to the bridging code or the router code for that protocol on that interface. If the protocol type is not supported, drop the frame. I don't know this, but I can reasonably assume that IP protocol identification is hard-coded for the Ethernet II IP Ethertype and for 802.2 IP. IP might be treated as a special case, of which the router is agnostic about encapsulation Still, the encapsulation should be meaningful if and only if appropriate routing or bridging is enabled for the interface. ARP has a protocol type field so that wouldn't seem like the reason. 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 et
RE: Another 802.3 and Ethernet Question
At 10:35 AM 2/7/01, Howard C. Berkowitz wrote:
I am also confused about the question itself.
The basic default behavior of Cisco routers is to try to identify the
protocol type of a frame, and send it either to the bridging code or
the router code for that protocol on that interface. If the
protocol type is not supported, drop the frame.
I don't know this, but I can reasonably assume that IP protocol
identification is hard-coded for the Ethernet II IP Ethertype and for
802.2 IP. IP might be treated as a special case, of which the router
is agnostic about encapsulation Still, the encapsulation should be
meaningful if and only if appropriate routing or bridging is enabled
for the interface.
That would be my assumption also. And, it is probably hard-coded to
recognize the EtherType for ARP also.
There were some cases of TCP/IP stacks using 802.3/802.2 and SNAP for IP
and ARP. They weren't very popular. But if you had some devices using them,
then you would have to configure the router to send ARPs that way. There is
also something called an HP Probe that accomplishes the same thing as ARP
in a non-standard way.
So there is an interface "arp {arpa | probe | snap}" command. I doubt that
it's used much. Encapsulation is much more of an issue for Novell.
This discussion has lost its steam. We might want to end it ;-)
Priscilla
ARP has a protocol type field so that wouldn't seem like the reason.
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,
RE: Another 802.3 and Ethernet Question
xed 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 _ 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 _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] Find the best deals on the web at AltaVista Shopping! http://www.shopping.altavista.com _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] _ 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 _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Another 802.3 and Ethernet Question
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 _ 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 _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] Find the best deals on the web at AltaVista Shopping! http://www.shopping.altavista.com _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] _ Do You Yahoo!? Get your free @yahoo.com address at http://mail.yahoo.com _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: Another 802.3 and Ethernet Question
My understanding of Ethernet having previously read RFC 1042 has been (as Anthony pointed out), that a router that receives 802.3 frames on an Ethernet interface will send out frames out using 802.3 encapsulation. A router that receives Ethernet_II frames on an Ethernet interface will send out frames using Ethernet_II encapsulation. If an end-system sends out 802.2 SNAP information within an 802.3 frame, would the router send this information within an Ethernet_II frame encapsulation? I've always thought that it wouldn't. Which leads to the question - why a default frame type, if the default frame type isn't used as an encapsulation frame type for creating Ethernet frames received by an end-system? Essentially, it's been my understanding that the default Ethernet_II frame encapsulation has been used where a packet originates within the router requiring a "first-time" Ethernet encapsultion. By that, I'm referring to telnet packets originating within the router - they need to be encapsulated in something as they go out an Ethernet interface. Alternately, packets received from a serial interface, token-ring interface, or FDDI interface that needs to be "popped-into" an Ethernet frame format would use the Ethernet_II encapsulation method. What benefit would it be to use an Ethernet 802.3 encapsulation rather than an Ethernet_II encapsulation method? You don't really get any benefit in my opinion. Ethernet_II has everything you need, and it's supported by all Ethernet devices since the inception of Ethernet_II equipment. It was just one of those things that made me go "hmm..." when I first stumbled onto the question... I think I think too much. (-: -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of anthony kim Sent: February 7, 2001 8:01 PM To: [EMAIL PROTECTED] Subject: Re: Another 802.3 and Ethernet Question Hi, I had to take a look at rfc 894 (ethernet) and rfc 1042 (ieee802) from rfc 1042: " It is possible to use the Ethernet link level protocol [12] on the same physical cable with the IEEE 802.3 link level protocol. A computer interfaced to a physical cable used in this way could potentially read both Ethernet and 802.3 packets from the network. If a computer does read both types of packets, it must keep track of which link protocol was used with each other computer on the network and use the proper link protocol when sending packets. One should note that in such an environment, link level broadcast packets will not reach all the computers attached to the network, but only those using the link level protocol used for the broadcast. Since it must be assumed that most computers will read and send using only one type of link protocol, it is recommended that if such an environment (a network with both link protocols) is necessary, an IP gateway be used as if there were two distinct networks. " ... then i read rfc1122: " Every Internet host connected to a 10Mbps Ethernet cable: oMUST be able to send and receive packets using RFC-894 encapsulation; oSHOULD be able to receive RFC-1042 packets, intermixed with RFC-894 packets; and oMAY be able to send packets using RFC-1042 encapsulation. An Internet host that implements sending both the RFC-894 and the RFC-1042 encapsulations MUST provide a configuration switch to select which is sent, and this switch MUST default to RFC- 894. " On Tue, Feb 06, 2001 at 10:34:21PM -0800, John Neiberger wrote: 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,
Re: Another 802.3 and Ethernet Question
On Wed, Feb 07, 2001 at 09:22:16PM -0700, Leigh Anne Chisholm wrote: [snip] Which leads to the question - why a default frame type, if the default frame type isn't used as an encapsulation frame type for creating Ethernet frames received by an end-system? The answer is mu. The default frame type means: the frame type the router uses at the Data Link layer when encapsulation has not been specifically defined. If you use the default encapsulation on a network for which the end systems are not configured, there will be no communication. You must manually configure the encapsulation to match the network's. If your real question is, why did cisco decide to use novell-ether has default? Or why did the IETF specify that Ethernet framing ought to be the default for IP networks, without looking up more references, I'd say it's largely historical and for backwards compatibility reasons. Essentially, it's been my understanding that the default Ethernet_II frame encapsulation has been used where a packet originates within the router requiring a "first-time" Ethernet encapsultion. By that, I'm referring to telnet packets originating within the router - they need to be encapsulated in something as they go out an Ethernet interface. Alternately, packets received from a serial interface, token-ring interface, or FDDI interface that needs to be "popped-into" an Ethernet frame format would use the Ethernet_II encapsulation method. Come on... you don't really believe this... 8^) [snip] It was just one of those things that made me go "hmm..." when I first stumbled onto the question... I think I think too much. (-: Best regards, Anthony _ Do You Yahoo!? Get your free @yahoo.com address at http://mail.yahoo.com _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Another 802.3 and Ethernet Question
Thanks! I had just never stopped to think too deeply about *why* different network-layer protocols would pick one ethernet frame type over another. John At 07:38 AM 2/5/01, John Neiberger wrote: 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, The default frame type depends on the payload. The default for IP is Ethernet V2 because the IP industry never adopted anything newer at the data-link layer. (They did adopt new physical-layer IEEE 802.3 standards.) Ethernet V2 has dest, source, and EtherType. If you were to change the frame type on the routers, you would have to change it on all IP hosts too, which would be a pain. Most operating systems (Windows 9x, Window NT, SunOS, Mac OS, etc.) default to Ethernet V2 for IP also. If you use AppleTalk Phase 2, the default frame type is 802.3 with 802.2 and SNAP. That's because all Macintoshes and other AppleTalk devices default to that frame type for AppleTalk also. (Phase 1 was Ethernet V2, by the way.) If you use Novell, the default is Novell "raw," aka Ethernet_802.3 which has dest, source, length, immediately followed by the IPX header which starts with an XNS checksum, which isn't used so it's always . The Novell default may have changed. I know Novell has been wanting to get with the rest of the world, plus they have been talking about actually using the checksum, which means they can't use the raw format. Also the raw format is kind of ugly because a "raw" frame arrives at a station configured for 802.3 with 802.2, the looks like a global LLC (802.2) SAP, which means "give this frame to all services!. Priscilla 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 ___ Send a cool gift with your E-Card http://www.bluemountain.com/giftcenter/ _ 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 ___ Send a cool gift with your E-Card http://www.bluemountain.com/giftcenter/ _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: Another 802.3 and Ethernet Question
John, What's the purpose of a default frame type? In IPX? What does the router do with other frame types not specified? Now what about with IP? What's the purpose of the default frame type? What does the router do with other frame types not explicitly specified? -- Leigh Anne -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of Priscilla Oppenheimer Sent: February 5, 2001 2:03 PM To: John Neiberger; [EMAIL PROTECTED] Subject: Re: Another 802.3 and Ethernet Question At 07:38 AM 2/5/01, John Neiberger wrote: 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, The default frame type depends on the payload. The default for IP is Ethernet V2 because the IP industry never adopted anything newer at the data-link layer. (They did adopt new physical-layer IEEE 802.3 standards.) Ethernet V2 has dest, source, and EtherType. If you were to change the frame type on the routers, you would have to change it on all IP hosts too, which would be a pain. Most operating systems (Windows 9x, Window NT, SunOS, Mac OS, etc.) default to Ethernet V2 for IP also. If you use AppleTalk Phase 2, the default frame type is 802.3 with 802.2 and SNAP. That's because all Macintoshes and other AppleTalk devices default to that frame type for AppleTalk also. (Phase 1 was Ethernet V2, by the way.) If you use Novell, the default is Novell "raw," aka Ethernet_802.3 which has dest, source, length, immediately followed by the IPX header which starts with an XNS checksum, which isn't used so it's always . The Novell default may have changed. I know Novell has been wanting to get with the rest of the world, plus they have been talking about actually using the checksum, which means they can't use the raw format. Also the raw format is kind of ugly because a "raw" frame arrives at a station configured for 802.3 with 802.2, the looks like a global LLC (802.2) SAP, which means "give this frame to all services!. Priscilla 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 ___ Send a cool gift with your E-Card http://www.bluemountain.com/giftcenter/ _ 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 _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
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 On Tuesday, February 06, 2001 at 08:45:48 AM, Leigh Anne Chisholm wrote: John, What's the purpose of a default frame type? In IPX? What does the router do with other frame types not specified? Now what about with IP? What's the purpose of the default frame type? What does the router do with other frame types not explicitly specified? -- Leigh Anne -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of Priscilla Oppenheimer Sent: February 5, 2001 2:03 PM To: John Neiberger; [EMAIL PROTECTED] Subject: Re: Another 802.3 and Ethernet Question At 07:38 AM 2/5/01, John Neiberger wrote: 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, The default frame type depends on the payload. The default for IP is Ethernet V2 because the IP industry never adopted anything newer at the data-link layer. (They did adopt new physical-layer IEEE 802.3 standards.) Ethernet V2 has dest, source, and EtherType. If you were to change the frame type on the routers, you would have to change it on all IP hosts too, which would be a pain. Most operating systems (Windows 9x, Window NT, SunOS, Mac OS, etc.) default to Ethernet V2 for IP also. If you use AppleTalk Phase 2, the default frame type is 802.3 with 802.2 and SNAP. That's because all Macintoshes and other AppleTalk devices default to that frame type for AppleTalk also. (Phase 1 was Ethernet V2, by the way.) If you use Novell, the default is Novell "raw," aka Ethernet_802.3 which has dest, source, length, immediately followed by the IPX header which starts with an XNS checksum, which isn't used so it's always . The Novell default may have changed. I know Novell has been wanting to get with the rest of the world, plus they have been talking about actually using the checksum, which means they can't use the raw format. Also the raw format is kind of ugly because a "raw" frame arrives at a station configured for 802.3 with 802.2, the looks like a global LLC (802.2) SAP, which means "give this frame to all services!. Priscilla 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 ___ Send a cool gift with your E-Card http://www.bluemountain.com/giftcenter/ _ 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 _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] -- www.tasmail.com _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: Another 802.3 and Ethernet Question
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 On Tuesday, February 06, 2001 at 08:45:48 AM, Leigh Anne Chisholm wrote: John, What's the purpose of a default frame type? In IPX? What does the router do with other frame types not specified? Now what about with IP? What's the purpose of the default frame type? What does the router do with other frame types not explicitly specified? -- Leigh Anne _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
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 On Tuesday, February 06, 2001 at 08:45:48 AM, Leigh Anne Chisholm wrote: John, What's the purpose of a default frame type? In IPX? What does the router do with other frame types not specified? Now what about with IP? What's the purpose of the default frame type? What does the router do with other frame types not explicitly specified? -- Leigh Anne -- www.tasmail.com _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: Another 802.3 and Ethernet Question
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 _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: Another 802.3 and Ethernet Question
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 _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: Another 802.3 and Ethernet Question
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 _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL
RE: Another 802.3 and Ethernet Question
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
RE: Another 802.3 and Ethernet Question
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 ___ Send a cool gift with your E-Card http://www.bluemountain.com/giftcenter/ _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: Another 802.3 and Ethernet Question
Hmmpondering 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 ___ Send a cool gift with your E-Card http://www.bluemountain.com/giftcenter/ _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] ___ Send a cool gift with your E-Card http://www.bluemountain.com/giftcenter/ _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Another 802.3 and Ethernet Question
At 07:38 AM 2/5/01, John Neiberger wrote: 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, The default frame type depends on the payload. The default for IP is Ethernet V2 because the IP industry never adopted anything newer at the data-link layer. (They did adopt new physical-layer IEEE 802.3 standards.) Ethernet V2 has dest, source, and EtherType. If you were to change the frame type on the routers, you would have to change it on all IP hosts too, which would be a pain. Most operating systems (Windows 9x, Window NT, SunOS, Mac OS, etc.) default to Ethernet V2 for IP also. If you use AppleTalk Phase 2, the default frame type is 802.3 with 802.2 and SNAP. That's because all Macintoshes and other AppleTalk devices default to that frame type for AppleTalk also. (Phase 1 was Ethernet V2, by the way.) If you use Novell, the default is Novell "raw," aka Ethernet_802.3 which has dest, source, length, immediately followed by the IPX header which starts with an XNS checksum, which isn't used so it's always . The Novell default may have changed. I know Novell has been wanting to get with the rest of the world, plus they have been talking about actually using the checksum, which means they can't use the raw format. Also the raw format is kind of ugly because a "raw" frame arrives at a station configured for 802.3 with 802.2, the looks like a global LLC (802.2) SAP, which means "give this frame to all services!. Priscilla 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 ___ Send a cool gift with your E-Card http://www.bluemountain.com/giftcenter/ _ 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 _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
