Pat Do wrote: > Are unintelligent 10 Mbps hubs better than unintelligent 10/100 > Mbps switches when the network cables that connect the PCs to > the hub or switch are Cat3 or Cat4? > > I provide network services to dozens of non-profits. Most of > the sites have Cat3 or Cat4 cabling. I have a co-worker who > says that 10 Mbps hubs should be used until the sites are > upgraded to Cat5 (which won't be happening any time soon). > > His rational: If the PC NICs are set to auto detect speed and > the unintelligent 10/100 switch is set to auto detect speed, > that data will try to pass through the Cat3 or Cat4 wire at 100 > Mbps. He says that while the data can pass thru the wire at > those rates, it's the signaling that gets scrambled at that > rate on a Cat3 or Cat4 wire. Consequently, to prevent > signaling problems that may in turn cause data integrity > problems, he's recommending to use 10 Mbps hubs. Is this a > valid argument?
Yes, it is a valid argument. If he's saying that autonegotiation will fail to negotiate because of the presence of Cat-3 cable, then he's wrong. The autonegotiation link pulses are simply bursts of the same Normal Link Pulses that have been used in 10Base-T for years. The pulses will travel over Cat-3 cable without any problems and the negotiation process will occur. However if he's saying that auto-negotiation will negotiate, but then you'll have problems, he's right. The problem is that the two devices will probably decide to use 100 Mbps. Auto-negotiation rules say that the devices should select the highest performance mode that they share in common. The result would be the NIC and switch port attempting so use 100 Mbps on Cat 3 cabling, which doesn't work. When we went from 10 Mbps to 100 Mbps we went from Manchester signal encoding to MLT-3 signal encoding to avoid the sorts of problems he is referring to. We also went to a requirement for Cat-5 cabling because of the increased frequency associated with the new signal encoding. > > Note: New, unintelligent 10 Mbps hubs appear to be becoming > less available and more costly relative to unintelligent 10/100 > Mbps switches as time goes on. Consequently, this issue is > starting to have financial implications. I know, isn't that annoying!? I like hubs. :-) Hubs have quite a few advantages for certain applications. As others have recommended, perhaps to avoid buying old equipment (hubs) that are getting harder to find (and more expensive), you could go with switches and hard code everything to 10 Mbps for now. But perhaps your point was that an _unintelligent_ switch might not let you configure hard-coded 10 Mbps instead of auto-detect. In that case, buy up a bunch of hubs, but don't beat me to it. ;-) _______________________________ Priscilla Oppenheimer www.troubleshootingnetworks.com www.priscilla.com Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=63391&t=63310 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
