VLAN stops passing traffic

[mhoppes]

I have had this issue on switches since way way way back in the beginning. I think since the start of the 1.5.x software branch where a vlan will just stop passing traffic -- not the port, it's not STP... just a vlan on the port will stop for about 8-10 seconds. Usually it's the management vlan of the switch, but I've seen it happen on other vlans from time to time.

When it happens, I can still ping the switch (on the same vlan and IP range as the other devices that I can't ping any more) but I will sporadically be unable to ping devices on that same vlan

e.g. VLAN 56. Switch at 10.200.56.5, devices at 10.200.56.10, 10.200.56.11, 10.200.56.12.

Device at 10.200.56.10 will randomly drop pings for 5-8 seconds. This isn't a device issue and it follows the switch and management vlan.
Log file on the switch and device show nothing and traffic continues to pass through the device (e.g. an AP to customers) just fine.

What's even weirder is devices ON the same vlan (e.g. the router at 10.200.56.1) can still ping the device when it stops passing traffic/pings but other devices that have to be routed in can not ping it. This is NOT a router issue though otherwise the entire subnet would stop working and it doesn't.

What is causing this, how can I figure out what's causing it?