Nexus 7000 and spanning tree design

[bmoore222]

Hello I have some non cisco routers running vrrp between three sites (Router 1, Router 2, Router 3.  The same server vlan resides at all three sites.  Currently spanning tree is blocking the link between Router 2 and Router 3.  I want to attach two nexus 7000s (connected currently to each other with vPC peer links) to router 1 and router 2 and also have this same server vlan reside on each nexus.  I am unsure the best way to link the two nexus's to Router 1 and 2.  

To vPc or not and where will spanning tree kick in with all of these different paths? 

 Note: I need to keep VRRP routing only between router 1, 2 and 3 as the existing network needs to be able to function without the Nexus's.  At some point the nexus's may be disconnected for an extended duration.

Thanks for the help

[Sam Byers]

Do the uplinks to the N7K's have to be L2? I like to use L3 when connecting blocks of networks.

You could go with the design you have. The N7K's run STP, and one of the two links added would be blocked. The same thing would happen if both R1 and R2 are connected to both N7k's with vPC's. The interfaces would just be port-channels.