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. 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!? Anyway, finding it will be hard, though there's good advice from Tom and others. I think I would revert to an old-fasioned communications channel. Announce over the loud speaker that if you just connected a wireless access point, disconnect it now and report to the office! :-) Priscilla Tom Martin wrote: > > Chris, > > STP should be enough to avoid these types of problems. In order > to cause > a bridging loop the station would have to have both interfaces > in the > same VLAN and forward all L2 traffic except for BPDUs. Even if > this were > the case the wireless network (10-Mbps?) shouldn't be enough to > bring > the LAN to its knees (100-Mbps?). If you have STP enabled on > all of your > switches, I'm doubt that a single station is bringing the > network down. > > Once you find the offending switch that you need to reboot, you > can > issue console commands to determine the root bridge and any > blocked > ports. Make sure that things are normal. You do have your root > bridge > set manually, don't you? :) > > To find out which port is causing the loop, take a look at the > interface > counters. You should see an unreal amount of traffic on the > offending > port (and the uplink to the core switch). > > When STP has been enabled I have only come across layer-2 loops > twice. > Once when a few HP switches had gone bad, and another time when > a > customer had configured channeling on one side but not the > other (3500 > series, no channel negotiation). > > In both cases I found that the problem was made worse with > increasing > traffic levels, and the problem also revolved around the same > set of > switches. The channeling problem was a bit more difficult to > narrow down > though, since it disabled MLS on the core switch and every > segment > appeared to have problems!!! > > I hope that helps, > > - Tom > > > Christopher Dumais wrote: > > Hi all, > > We are having an STP problem where we think a user with an > integrated > > wireless and LAN NIC is creating a bridge loop and bringing > down the entire > > network. The problem occurs then goes away after 20 or so > minutes unless we > > can narrow down which closet it is coming from and reboot the > switch. All of > > our management tools die during the outage. Does anyone have > any ideas on > > how we might prevent this from happening or track down the > offender? We have > > 6509's in our Core and a mix of 3548's and 3550-SMI. Any > thoughts are > > appreciated. Thanks! > > > > Chris Dumais, CCNP, CNA > > Sr. Network Administrator > > NSS Customer and Desktop Services Team > > Maine Medical Center > > (207)871-6940 > > [EMAIL PROTECTED] > > Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=70821&t=70797 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
