STP in non-vPC links connecting to a vPC N5k

[student100]

Hello:

I'm having trouble figuring out which ports would be blocked by RSTP in the attached topology, because I've read that the peer-link never-ever blocks, not even from a non-vPC devices/links point of view.

Nexus 5K form a vPC for FEX connection. Upstream, they connect with common portchannels to the switches 6500, as shown. One of those 6500 is the root.

I would like to know:

1) From the non-vPC devices point of view, does the peer-link never blocks? Not even if I change its cost (if possible...) ?

2) Is it possible to change a Po STP cost?

3) In the shown topology, which port channels would get blocked?

4) How would the FEXs be affected by the resulting STP topology (since vPC peer-link is forbidden for their traffic)??

Thank you in advace for your help!

[student100]

Hi to all with a similar problem:

Since i didn't get any answer in this forum, I asked a TAC engineer, so I'm attaching the resulting STP topology. As you can see, one Nexus has two root ports (which we can read in some design guides), but being so, the peer link is used for traffic ONLY if any other uplink is not available, eventhough the peer-link is always active.

Hope this helps.