We have bridges installed in different locations and the root bridges are connected to our switches. The problem is, when the STP on the root bridge is not enabled, I cannot ping it, but all the non-root bridge is ping-able and can browse the network.
Most probably this is due to excess bpdu that are exchanged between switches for establishing root bridge. These will choke the links and hence you're getting no response. I would suggest that you tweak your STP further. All non-root bridges should be forced not to take part in STP calculations. Set their priority to zero. For each VLAN, set only one switch/bridge as root all and the other should have their priority set at zero.
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