Creighton Bill-BCREIGH1 wrote: > > Give me a cross-over cat5, a couple hubs, and a clustered > server with a dual > NIC card having each interface to each respective hub and I'll > bet I can > make the hubs go into a loop...
Yes, indeed, that's a loop also. I was going to mention this example too, but took it out at the last minute. The difference here is that the server doesn't forward the bits (hopefully!) If the server forwarded the bits (like a hub would), there would be no stopping of the bits and the network would be hosed. Priscilla > > -----Original Message----- > From: Priscilla Oppenheimer [mailto:[EMAIL PROTECTED]] > Sent: Monday, December 09, 2002 12:10 PM > To: [EMAIL PROTECTED] > Subject: RE: Dumb question [7:58783] > > > Jay Dunn wrote: > > > > A "hub" or "repeater" operates at layer 1 and makes no > intelligent > > decision about what to forward. A packet enters a port and is > > forwarded > > out all other active ports on the hub. The concept of a loop > > only exists > > at higher layers. > > A loop could exist at the physical layer too. A newbie could > connect the > hubs in such a way that there was a loop. And it could indeed > cause problems > due to the fact that a hub doesn't make any intelligent > decisions about what > it forwards, as you say, and doesn't participate in higher-layer > loop-avoidance solutions such as STP, Dijkstra, split horizon, > etc. There > would be nothing to stop the looping bits. The very idea makes > me cringe. > :-) > > It's kind of funny that nobody thinks about this. A network of > hubs must be > designed in a hierarchical fashion. I guess that is just > second-nature to > people who grew up with hubs. > > When hubs entered the market they allowed us to move away from > the > ubiquitous bus topology and into a star (hub-and-spoke) > topology. They > allowed us to start using the structured cabling that AT&T and > other vendors > were starting to install, rather than the Christmas-tree-lights > topology so > popular with coax cable and so prone to problems. As networks > grew, it > became necessary to connect multiple hubs. The term that was > often used was > "cascating hubs." Hubs cascaed from other hubs, within the > rules related to > Ethernet propagation delay and collision detection. > > Priscilla > > > > > Jay Dunn > > IPI*GrammTech, Ltd. > > www.ipi-gt.com > > Nunquam Facilis Est > > > > -----Original Message----- > > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]] On > Behalf > > Of Han Chuan Alex Ang > > Sent: Monday, December 09, 2002 3:44 AM > > To: [EMAIL PROTECTED] > > Subject: Dumb question [7:58783] > > > > I am wondering if Hub could be subjected to loop problems , > if not, > > what will happen if there is a loop within a Hub enviroment > > Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=58812&t=58783 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
