STP and VLAN Trunk Ports?

[karl_009]

Hello,

I have been going over the ICND 1 & 2 CBT while am doing that I have my own lab, 3 switches 4 routers.

My question is about spanning-tree and vlan trunking ports.

I have SW1 SW2 and SW3.

SW1 connects to SW2 and SW3, I have placed a redundant link between SW2 and SW3.

The ports that connect SW1 to SW2 and SW3 are trunk ports, however the link between SW2 and SW3 is just an access port.

I am running Rapid PVST+.

I have vlans 10, 20, 30 each switch has ports assigned to each vlan.

I am also running router on a stick to route between the vlans.

Why, when I disconnect SW1 from SW2 am I still able to communicate with the computers in the same vlan between two switches, I thought all links between switches had to be trunk ports when communicating with vlans yet my redundant link is just an access port.

Or have I missed something.

Thanks

Karl

[glen.grant · Accepted solution]

  If the traffic is in the same vlan as the crosslink they would be able to talk ,  but intervlan traffic should be broken between SW2 and SW3 .  I am going on the assumption the router on a stick is connected to SW1.

[InayathUlla Sharieff · Accepted solution]

Hi Karl,

AS Glen said that it has connectivity between the SW2 and SW3 and SW3 has the link to SW1 you should have good connectivity between the vlans as they have allowed vlans on the trunk ports.

Regards

Inayath

[karl_009]

Hello,

Thanks for your replies, with your feed back I took a closer look at my designs and done some further testing.

That testing has now answered my question that any of my redundant links must also be trunk ports to ensure some semblance of normal network operations continues.

Thanks again for the feed back.

Karl