[VLAN] STP+VLAN

[sameer.neugui at tatainfotech.com (sameer)]

Hi all,

I am basically facing a problem with STP. But since STP is related to VLAN
in some respect I guess there would be someone here who can help me.

Background:

We have developed a layer two switch. This uses Cirrus logic's ep9301
processor, embedded Linux 2.4.21 kernel as the OS and zarlink's switch
controller.

The observation:

1)we have 2 switches, switch A and switch B

2)port 1 and port 2 of switch A are connected to port 1 and port 2 of switch
B

3)1 PC is connected to port 0 of switch A and another to COM port of switch
A to observe STP

4)We restart the 2 switches and observe that one of the links is blocked and
the other in forwarding state. STP is always enabled on reboot

6)We start to ping switch A and the switches and the two PC hang.

7)the LEDs on the switch device that signify the activity are seen
continuously glowing.

8)switch A and B, PC 1 and 2 cannot be accessed at all.

9) We remove one of the links and the STP reconfigures and the switch A can
be pinged.

10)Most of the time we have observed, although not a confirmed pattern, that
if we remove the blocked link, the STP just disables the port on switch A
(we have not observed the counter part on the switch B

11)Neither the switches nor the PCs were on the rest of the company network

Its not a hang exactly as upon some topology change the system is back to
working. I also checked on the internet. On cisco site I found something
called unicast flooding. Is this the reason for the system to blog down?
what would be the fix or some pointer in this regard?

Please help.

Sameer