My hub is calling me to dinner so I have to make this quick. The access point that I'm most familiar with is the Apple airport. It's essentially a router. It connects 2 subnets and does DHCP and NAT.
It can also be put into bridging mode, in which it is transparent and connects devices in the same subnet. I doubt it does STP. I hadn't noticed that the originial poster said wireless NIC. That seems sort of unlikely to cause major problems I agree. I sketeched out some simple loops though. They certainly could happen. Wish we had whiteboard capability on GroupStudy. Gotta run. The hub made dinner! :-) Priscilla The Road Goes Ever On wrote: > > ""Zsombor Papp"" wrote in message > news:[EMAIL PROTECTED] > > At 08:34 PM 6/17/2003 +0000, Priscilla Oppenheimer wrote: > > >Access points can be configured to do bridging and I > wouldn't be > surprised > > >to discover that they don't do STP, especially low-end ones > from the > local > > >KMart. A lot of low-end switches don't do STP either. > > > > Yet they filter out BPDUs? If they don't, then assuming proper > > configuration on the "high end" switches, can there be really > loop? > > > > > So, the access point > > >would have to be inserted into the network just right so > that it caused a > > >loop, but that's certainly possible. In that case all the > looping > broadcast > > >traffic, not to mention looping unknown unicast traffic, > could bring a > > >network to its knees. > > > > > >I'm surprised so many people doubted his decription of the > problem!? > > > > A 6509 can switch multiple gigabits of traffic without any > problems. You > > would need quite a few wireless loops to kill such a box. I > might be > > missing something but I still doubt that "a user with an > integrated > > wireless and LAN NIC" can kill bring down a network of 6509 > and 3550 > > switches. > > > Not knowing firsthand, I've checked the Cisco documentation. > For the 1200 > series of AP's, at least, I can find no reference to spanning > tree. Not > saying it isn't there. Just saying I see no reference. > > every AP with which I am familiar has but a single ethernet > port. It is > essentially a hub, although some of the vendors have some pretty > sophisticated capability build in as part of their firmware and > OS. I've > been working with Proxim on a deal, with 802.1x port based > authentication. > The particular Proxim device creates virtual ports for end > stations, and > communicates with radius to ensure that the user can > authenticate against > the 802.1x database, even as the user moves from AP to AP. > > It is not inconceivable that putting in a series of wireless > AP's could > create a loop somewhere. Particularly if there are rogue > devices out there > and someone is wandering among them. Just thinkking out loud, > but the switch > would see a user MAC comming into different ports as the user > moved around. > > Thinking out loud again, with an authorized and reasonably > thought out > wireless installation, all your AP's would be in the same > subnet/vlan and > users wandering from AP to AP would cause no problems becasue > to the back > room switch the user mac would be on the same vlan as it moves. > as far as > the switch is concerned, nothing untoward has happened. > > Unless something is terribly wrong - i.e. major bug in the AP > software - > users cannot be connected to more than one access-point > simultaneously ( if > they could, that might cause loop problems ) generally, the > wireless nic > firmware negotiates connection to the AP with the strongest > signal in a > mobile situation. > > Once in a while I see a comment that leads to believe that > there may be some > misunderstanding about the term "bridge" when used in > conjunction with > wireless. > > A wireless bridge is a device for point to point wireless > communication with > another wireless bridge. It is more like a serial link than > what most folks > think of when they hear the term "bridge". one of those > newfangled terms > that is in the purist sense misused, but neverless is used > differently than > in the world of switches. > > So, one way for wireless, with it's single ethernet port, to > create a loop > would be for it to bridge to anther AP, which in turn is > plugged into the > same switch. Loops would form and the ensuing broadcast storm > could wreak > havoc. > > > > > > > > > > Thanks, > > > > Zsombor > > Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=70836&t=70797 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
