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Hi Deanwebb,

Let me rephrase my question.  VLAN will create a broadcast domain for all packets. 
But for STP BPDUs all the ports irrespective of VLAN will be a broadcast domain.

Can you please tell if there is any configuration that can be made on switch so that the broadcast domain of VLAN will be applicable for STP BPDUs also.

Thanks
uv.

I have a router platform with STP enabled on it.  If I connect Router.Eth2 and Router.Eth3 to a single 8port switch, router blocks one port.  If I connect to two separate 8port switches, both of them are in forwarding state.

Attachment Image: 2-switch.jpg

I am using one Cisco SG300. I am trying to simulate the above case using VLANs.

Attachment Image: vlan-switch.jpg

My requirement is to satisfy the following conditions:

1. When I connect, Router.Eth2 to port 3(VLAN2) and Router.Eth3 to port 5(VLAN2), Router.Eth2 and Router.Eth3 should be forwarding.

2. When I connect, Router.Eth2 to port 3(VLAN2) and Router.Eth3 to port 4(VLAN2), one of the Router.Eth2 and Router.Eth3 should be blocked.

In SG300, Spanning Tree state 'Disabled', STP Operatin Mode as 'Multiple STP' and 'BPDU handling' as filtered.  When I did connection (1), Router.Eth2 and Router.Eth3 are in forwarding state.  In connection(2) also, Router.Eth2 and Router.Eth3 are in forwarding state.

In SG300, Spanning Tree state 'Disabled', STP Operatin Mode as 'Multiple STP' and 'BPDU handling' as flooding.  When I did connection (1), Router.Eth2 and Router.Eth3 are blocked.  In connection(2) also, Router.Eth2 and Router.Eth3 are blocked.

Can someone help me in making necessary configuration on SG300, to make my requirements meet.

Thanks in advance.
uv.