I just noticed that I misplaced the functional/non-functional bit. I hate that! ;-)
The functional/non-functional bit is the most significant bit of the 3rd byte (not the least significant bit of the 2nd byte as I said before.) So, the address is: 4000.a089.0002 01000000 00000000 10100000 ... First bit transmitted (most significant of 1st byte) is 0 (specific) Second bit transmitted is 1 (locally-administered) Most significant bit of the third byte is 1 (non-functional) That makes more sense now that I see he was referring to a source address. A source address shouldn't be a functional address. Priscilla At 01:17 PM 5/23/02, Priscilla Oppenheimer wrote: >At 07:25 AM 5/23/02, Ivan wrote: > >Hi all, > > > >I have a interest question, doesn't any one know the answer? > > > >A router is being used as a translation bridge between a Token Ring network > >and an Ethernet network. Host X on the Token ring sends a packet to Host Y > >on the Ethernet. The soursce MAC address of the packet is 400.a089.0002. > >That's not a valid address. A MAC address is 48 bits or 6 bytes. In hex a >byte is written with 2 digits. So the address must have 12 digits. > >I assume you are missing a 0 and that you meant to say: 4000.a089.0002 > >The bridge will translate the non-canonical address to canonical (see my >other message and numerous other messages on that computing 101 topic). > >On the other hand, maybe the question expects you to know these other >details: > >The first byte of that address in binary is: > >01000000 > >Token Ring transmits the most significant bit first. (the one in the 2^7 >position). > >IEEE says that the first bit transmitted is the Specific/Group bit. (A >group address is used for multicast and broadcast). > >0 = Specific >1 = Group > >So this is a specific address. No problem. Ethernet can handle that (and >could handle a multicast or broadcast too, of course.) > >IEEE says that the second bit transmitted is the Globally >Administered/Locally Administered bit. > >0 = Global >1 = Local > >So this is a locally-administered address. Although IEEE 802.3 (Ethernet) >does officially support locally-administered addresses, they aren't often >used on Ethernet. So that's a minor issue. > >The second byte is >00000000 > >IEEE 802.5 (Token Ring) says that the least significant bit of the second >byte is the Functional/Non Functional address. IEEE 802.3 (Ethernet) does >not say this and does not support functional addresses. > >0 = Functional >1 = Non functional > >So here we have a slightly more interesting issue. This is a functional >address. Ethernet won't recognize that it's a functional address, however. > From a troubleshooting viewpoint, you would want to figure out what >"function" this was supposed to carry out on the Token Ring side. Whatever >it was, it's not going to also get carried out on the Ethernet side. For >most functional addresses, this isn't an issue. The well-known ones are >used for purposes such as: > >Sending to the active monitor (which doesn't exist on Ethernet) >Sending to the ring parameter server (which doesn't exist on Ethernet) >Sending to LAN manager (which doesn't exist on Ethernet) >etc. >You get the picture > >This particular address is one that I don't recognize though. It may be >used for a proprietary (non-standard) function on the Token Ring side. > >Perhaps you are expected to know these sorts of things to answer this >question correctly. > >Priscilla > > > > How > >would the MAC address be interpreted in an Ethernet environment? > > > >does anyone know the answer? thank you. > > > >Ivan >________________________ > >Priscilla Oppenheimer >http://www.priscilla.com ________________________ Priscilla Oppenheimer http://www.priscilla.com Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=44852&t=44805 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
