6200yl-24G-mGBIC Freezes up new fiber-optic network

[thomasp942]

I have a 6200yl-24G-mGBIC switch connected to 8 Procurve 1810G-24 switches via new 50ohm fiber-optic lines. When I power up the 6200yl switch I get steady green leds on all the ports, and a very rapid activity light on the 1810G-24 switches. However nothing can communicate across the network, I can't even ping from a server to the firewall which are both in the rack on the same switch, and it takes workstation about 4 times longer to log in, but when they do they don't see the domain. All the switches are still on factory settings, I have been using the 1810G-24 switches for almost a year on an old ethernet "daisy chained" network, but this is the first that I'm powering up the fiber. Anyone have any ideas what the problem is?

[Pieter 't Hart]

I assume the 1810's are allready interconnected before installation of the 6200?

by default spannig-tree is disabled.
So you create loops in your network when powering up the 6200.

-> disconnect all 1810's before powering up the 6200.
- then connect a single 1810 using a single Fibre (pair).
- see network behaviour (probably all normal)
- connect a second 1810
-> now the netweork will go bezerk again
=> spanning-tree problem configred
(disconnect again)

==>> either enable and configure spanning-tree.
or disconnect the old 1810's uplink before connecting to the 6200.