Although I agree that three "Layer 2 hops" is best, as Cisco recommends (core, dist, access), I also can't understand why the scenario you describe above is causing a problem (assuming the spantree roots are set properly, etc. be careful that one of the 1900s isn't the root bridge for a VLAN =) I don't really see the number of Layer 2 hops as being a problem. About the only problem I could see is if one of the switches along the line is getting overloaded with traffic. Given the information you provided, there could be a couple of "weak links". If one assumes the max throughput of a hub is around 4Mbps, then each 1900 would have 4-8 * 4Mbps = 16 - 32Mbps on each 1900. Each 3500 has 8-12 1900s (let's say 10), so each 3500 has 160-320Mbps, no problem. But then Each 5000 has 10-12 3500s (again, let's say 10), which is 1.6-3.2Gbps. This could be a problem for the 5000 and it's 1.2Gbps backplane. That's weak link #1. Also, assuming the 5000 isn't being overloaded, even being generous, the 100Mbps links between the 5000s and 5500s are definitely a weak link. At that point you have the equivalent of roughly 600 (10 3500s * 10 1900s * 6 hubs = 600) 10Mbps hubs trying to jam through a single 100Mbps link. Even if each hub os only using .3Mbps (less than DSL/Cable modem speeds), that's still almost 200Mbps trying to jam through 100Mbps link from the 5000 to the 5500 (assuming most of the traffic is destined for the internet, or a destination being routed by the 6500(r), etc) IMHO, those two "weakness" are 100 times more likely to be causing problems than the number of Layer 2 hops involved, again assuming STP is configured correctly. Once the 5500s uplink into the 6500s, it's virtually impossible for those 5500s to overload the 6500 (and it's default 32Gbps backplane), especially since (according to our Cisco rep) the Gig ports on the 5500 deliver no where near actual 1Gbps performance.
So, in a nutshell, IMHO, bandwidth, not the # of layer 2 hops, is more likely causing your problems. Just my 2 cents. =) Mike W. Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=38607&t=38453 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
