I totally believe you all...just I used to Think that Pine Mountain group knew what they were talking about and their web site classifies all of the below as bcast. perhaps I'll let them know :) thanks
""Brian Backer"" wrote in message news:[EMAIL PROTECTED]... > Priscilla, > > Weird... all the documentation I have seen says that a BPDU is a > broadcast just like CDP and HSRP... My friend, I believe you are mistaken. "CDP sends packets on LANs using the multicast address 0100.0CCC.CCCC" http://www.cisco.com/univercd/cc/td/doc/product/lan/trsrb/cisnm.htm#xtocid18 4495 "Each device configured for CDP sends periodic messages, known as advertisements, to a multicast address." http://www.cisco.com/univercd/cc/td/doc/product/software/ios121/121cgcr/fun_ c/fcprt3/fcd301c.htm "HSRP works by the exchange of multicast messages..." http://www.cisco.com/univercd/cc/td/doc/cisintwk/ics/cs009.htm#xtocid122331 "Routers that are participating in an HSRP group communicate to each other via a multicast User Datagram Protocol (UDP)-based hello packet" http://www.cisco.com/warp/public/cc/so/cuso/epso/entdes/hsrp_wp.htm "The Destination MAC address uses the well-known STP multicast address of 01-80-C2-00-00-00" - Cisco LAN Switching, Clark and Hamilton, page 184. > b > > > > -----Original Message----- > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]] On Behalf Of > Priscilla Oppenheimer > Sent: Monday, June 17, 2002 9:33 PM > To: [EMAIL PROTECTED] > Subject: Re: STP BPDUs [7:46839] > > BPDUs are sent to a multicast address that means "all bridges." In > Ethernet, they are sent to 01:80:C2:00:00:00. For the destination > address > on Token Ring, reverse the bits, one byte at a time to get > 80:01:43:00:00:00. > > At 08:39 PM 6/17/02, Tim Potier wrote: > >This might be a simple answer, but what type of message is a BPDU: > >Unicast, Multicast or Broadcast. I have searched all over Cisco's > site, and > >dug through STP RFC..no luck. > > It's not an RFC. It's IEEE 802.1D. See here: > > http://standards.ieee.org/getieee802/ > > > I have come up with the following: > > > >"The Destination Address field indicates the destination address as > >specified in the Bridge Group Address table. For IEEE Spanning-Tree > Protocol > >BPDU frames, the address is 0x800143000000. > > That is bit-reversed. You must have found a document that covers Token > Ring. > > > For IBM Spanning-Tree Protocol > >BPDU frames, the address is 0xC00000000100. > > IBM had their own version of STP. DEC also had a variety of STP. They > sent > to the broadcast address (FF:FF:FF:FF:FF:FF). > > >For Cisco Spanning-Tree Protocol > >BPDU frames, the address is 0x800778020200." > > Cisco spanning tree? What is that?? Something to do with the Per VLAN > Spanning Tree (PVST) on Token Ring?? (Once again, that looks like a > Token > Ring multicast address.) On Ethernet, PVST uses the standard destination > I > think, unless you use PVST+ which tunnels PVST BPDUs through an 802.1Q > Mono > Spanning Tree implementatoin, thus allowing each VLAN to maintain its > own > spanning tree. Cisco uses the multicast address 01:00:0C:CC:CC:CD for > PVST+ > on Ethernet. Bit reverse that and you don't get 0x800778020200, however, > so > I don't know what that adddress is for. > > >I guess it also depends on the definition of multi/broad/unicast. > > It better not depend on that. There shouldn't be any argument on those > definitions. ;-) > > Multicast means a group address. The first bit of the destination MAC > address (which is the first bit transmitted) is a one so that every > device > knows to look at the address. A NIC driver software supports an > application > telling the NIC which particular multicasts to take in. > > Broadcast means every device in the broadcast domain. The first bit and > all > bits in the MAC destination address are ones. Every NIC in the broadcast > > domain takes in the frame and interrupts the host CPU to see if the rest > of > the frame is interesting. > > Unicast means a specific address. The first bit of the destination MAC > address (which is the first bit transmitted) is a zero. > > HTH > > Priscilla > > > >Thanks for your help. > ________________________ > > Priscilla Oppenheimer > http://www.priscilla.com [EMAIL PROTECTED] Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=46886&t=46839 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
