Switch – Does Gigabit degrade all ports to 100 megabit if there is a 100 megabit device attached

Maybe the switches were just in awe of your amazing topology?

Seriously though, if you can take the time, do it again, but only connect one switch at a time to the Gb switch, and verify connectivity and function at each step.

When the network finally halts, disconnect all of the switches, and try connecting that switch first. If it does it again, disconnect everything on that switch and add them back, one by one to find the unhappy link.

If it doesn't die, add switches until it does. If it fails after adding more switches, maybe one of the switches can't handle the size of the MAC address table, and you need a bigger switch?

Ok here's another data point for you from a PowerConnect 5324. Which is a few generations behind the models you're looking at. So take it for what it's worth.

So the ping command below was sending 1 ping per second to you can see from the output below that it took 108 seconds from the point where it went down from the reload command to the point that it started replying again.

PowerConnect 5324 reboot 108 seconds

date && ping 192.168.0.2 && date
Thu Apr 15 00:06:45 EDT 2010
PING 192.168.0.2 (192.168.0.2) 56(84) bytes of data.
64 bytes from 192.168.0.2: icmp_seq=1 ttl=64 time=2.53 ms
64 bytes from 192.168.0.2: icmp_seq=2 ttl=64 time=2.54 ms
64 bytes from 192.168.0.2: icmp_seq=3 ttl=64 time=2.55 ms
64 bytes from 192.168.0.2: icmp_seq=4 ttl=64 time=2.60 ms
64 bytes from 192.168.0.2: icmp_seq=5 ttl=64 time=2.55 ms
64 bytes from 192.168.0.2: icmp_seq=6 ttl=64 time=2.76 ms
64 bytes from 192.168.0.2: icmp_seq=7 ttl=64 time=2.50 ms
64 bytes from 192.168.0.2: icmp_seq=8 ttl=64 time=2.63 ms
64 bytes from 192.168.0.2: icmp_seq=9 ttl=64 time=3.51 ms
....
64 bytes from 192.168.0.2: icmp_seq=117 ttl=64 time=2026 ms
64 bytes from 192.168.0.2: icmp_seq=118 ttl=64 time=1028 ms
64 bytes from 192.168.0.2: icmp_seq=119 ttl=64 time=30.1 ms
64 bytes from 192.168.0.2: icmp_seq=120 ttl=64 time=3.80 ms
^C
--- 192.168.0.2 ping statistics ---
120 packets transmitted, 13 received, +45 errors, 89% packet loss, time 119202ms
rtt min/avg/max/mdev = 2.502/239.520/2026.970/583.213 ms, pipe 4
Thu Apr 15 00:08:45 EDT 2010