There are other systems that allow you to change the Ethernet encapsulation, for example Juniper routers:
set interfaces fe-0/0/0 unit 0 encapsulation dix set interfaces fe-0/0/0 unit 0 encapsulation 802.3-llc set interfaces fe-0/0/0 unit 0 encapsulation 802.3-snap I think I've also seen it on Ericsson systems. > > But for some reason you can't directly configure SNAP for IP. > In the past hosts connected to 10BaseT networks conformed to the following rules: 1. must be able to send and receive IP packets according to RFC 894; 2. should be able to receive RFC 1042 packets, intermixed with RFC 894 packets; 3. may be able to send RFC 1042 packets. Default however is RFC 894. RFC 894 Standard for the transmission of IP datagrams over Ethernet RFC 1042 Standard for the transmission of IP datagrams over IEEE 802 So the default (within IETF) was/is Ethernet II (DIX). Most(?) systems did not allow you to configure SNAP for IP directly, since it wasn't mandatory in the standards. However, if they received SNAP frames, they started responding with SNAP frames. Eric ----- Original Message ----- From: "Priscilla Oppenheimer" To: Sent: Tuesday, July 01, 2003 5:49 PM Subject: Re: encap for ethernet interface ? [7:71681] > Cool! I was wondering if someone would come up with that one. You can > configure ARP for SNAP which causes the router then to use SNAP for IP if it > gets a response. But for some reason you can't directly configure SNAP for > IP. And, as you say, that's for Ethernet (not Token Ring which by default > uses SNAP for IP). > > You might enjoy my Ethernet lab scenario here: > > http://www.troubleshootingnetworks.com/ethernet.html > > It mentions that. > > Priscilla > > [EMAIL PROTECTED] wrote: > > > > "Priscilla Oppenheimer" wrote: > > > > >> To establish Ethernet encapsulation of IP packets, use one of > > >> the following > > >> commands in interface configuration mode: > > > > >The document says that you can change the encapsulation for IP > > packets? > > You > > >can't do that on my routers! There's no need to do it anyway. > > There is > > >essentially no modern operating system that doesn't use > > Ethernet II for > > IP. > > > > >I'd be interested to see if anyone else is able to change the > > Ethernet > > >encapsulation for IP packets on their routers." > > > > IBM used to sell an interface card for OS/390 mainframes with > > two ports, > > each configurable for 16Mbps Token Ring or 10Mbps Ethernet. I > > think they > > were sold in the late nineties. Even when configured for > > Ethernet, SNAP is > > used for IP. I had one of these - it would only start working > > if the > > mainframe issued the ARP. The router would recognise the ARP in > > a SNAP > > frame and continue to use SNAP. If the router ARP'ed first, it > > used an > > Ethernet II "arpa" frame and received no reply from the > > mainframe. A > > correspondent on IBMTCP-L recommended setting the ethernet > > encapsulation > > to SNAP on the router but the encapsulation command didn't > > work on my 12.1(5)T7 3660. I didn't try arp snap, and I haven't > > got the card anymore to test > > with. > > > > Jenny Margrison > > > > > > Important: This e-mail is intended for the use of the > > addressee and may contain information that is confidential, > > commercially valuable or subject to legal or parliamentary > > privilege. If you are not the intended recipient you are > > notified that any review, re-transmission, disclosure, use or > > dissemination of this communication is strictly prohibited by > > several Commonwealth Acts of Parliament. If you have received > > this communication in error please notify the sender > > immediately and delete all copies of this transmission together > > with any attachments. Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=71746&t=71681 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
