will loop happen and spanning tree will work?

[Lasandro Lopez]

i've one access switch, layer2, unmanaged (just plug and play) that connects internal users pc.

above that, i've to core switches L3, managed one.
I want to connect the layer2 switch, with two paths for redundancy links

one link from layer2 to Core01

another link from layer2 to Core02

My questions are:

1. Will the loop happen?

2. If he "primary line" between layer2 switch and the core01 is failed (or the core01 is failed), will the link be active via the link Core02?

Let me know!

Regards!

[Gregory Snipes]

It depends on how your layer 3 switches are configured. Are the ports on the devices set to: trunks, access, or routed? If they are set to trunk or access, is there any layer 2 connectivity between the two layer 3 switches, i.e. a trunk?

[Lasandro Lopez]

The ports that connect two core switches, are set to trunk.

how i've to configure the ports between core switches and Layer2 switch (trunk or access)?

[Lasandro Lopez]

So any news!

Here is the diagram, so i want to know if loops happen or not.
Regards!

[blau grana]

Hello Lasandro,

Cisco switch ports toward L2 switches should be configured as access cause I do not think that unmanaged switches will support 802.1q.

L2 loops should not occur if L2 switches will not filter BPDUs from cisco switches, but you have to test it, cause I am not sure how will these switches behave.

Best Regards

Please rate all helpful posts and close solved questions

[Renan Abreu]

There are a lot of ways to check that. Issue show spanning-tree vlan x and check how the ports are behaving,

place a HUB in the middle of the conversation or configure SPAN and check if BPDUs are being sent, if they are you are STP capable, if they're not, you'll probably have problems because both core switches will most likely be able to see each other.