1. I've got 6 AT-8326GB switches. 2. They have all got the latest firmware and have got a factory reset. 3. I have tried swapping the switches around - so it isn't a fault with one switch. 4. I've given the master switch and IP address (no other configurations are made). I'm trying to stack them together (using the back cables), but am having problems: If I connect a PC to the master and ping it - it works fine. If I connect the PC to any of the 5 slave switches and ping the master I get very slow response times (~800ms). I can ping a server attached to the master switch OK (1ms), but the customer has complained about intermittent network problems - which may be related? However, if I connect the switches using Cat5 cables on the front gigabit ports, it works fine (pings in ~1ms). I have tried replacing the back cables with new ones, but no joy. Q. Can the fact that pings to the master switch take ~800ms affect the performance of the network? Q. How can the back connections on all 6 switches be faulty? I've got an identical stack elsewhere, and it works fine.

Q1 yes that can effect the network Q2 doubt they are faulty as much as misconfigured since it appears you have the problem with any two connected. What revision are you on for the stack that is working fine? Same or different? If different downgrade to that firmware. Why aren't you giving every switch a ip address since these appear to be managed switches? Since these appear to be managed switches what is the configuration options? Spanning tree available? Port settings for the uplinks? Golly gee wilerkers everyone! Learn to Internet Search