Re: STP+VLAN

On 7/27/05, sameer <[email protected]> wrote:
> 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?

Sounds to me like the link that is "blocked" isn't really blocked and
you're getting a loop.

Jason