STP a Problem or Not?

[Daniel Mohammed]

Hi,

I am not sure if i should be concerned or not here - STP has never been my strong point. 

I have two core switches connecting together via lacp. Each core switch has single connections to access layer switches. The access switches just run layer 2, and vlans are trunked between core and access.

Now there is vrrp running between the two core switches, so each access switch can respectively get to the GW through its uplink to the core. My question is this, and sorry if i am missing something basic, but...

If One of the core switches becomes the route bridge, then the other core switch may fall into a situation where it has to block one of its port (put in a state of discarding) - (i know it wont block the ae but a link to an access switch it might block), if that is the case the one of the links to an access switch will essentially have no route to the GW? is that correct? and if so what is a away to avoid this?

You'll notice that i have also show VLAN100 which is essentially existing links to an old network, i have included this as it shows there is still some sort of loop in the connection albeit on a different vlan.

Thanks

[Georg Pauwen]

Hello,

I would configure rapid pvst+ only for Vlan 100, since that is apparently the only one that has dual connections to both SW1 and SW2. For good practice, I would configure SW1 as the primary root switch for Vlan 100, and SW2 as secondary root.

So, on all participating switches, configure:

Switch(config)#spanning-tree vlan 100

And on SW1:

SW1(config)#spanning-tree vlan 100 root primary

On SW2:

SW2(config)#spanning-tree vlan 100 root secondary