WAN Routing between N5K (L3-vPC) & VSS (MEC) with Link Aggregation

Question:

We want a solution for Cisco 3925 price  routing between N5K and VSS with aggregated WAN links. Here is the scenario.

DC1: It has 2 cisco 6509 with VSS. There are 4 server farm cisco4948 switches connected with VSS with redundant uplink via MEC. Server gateway is the VSS. VSS is running Eigrp routing.

DC2: This is a new datacenter we are going to establish soon. We are planning 2 N5K at core layer with L3 daughter card and 4 N2K as server farm switch. 2 N5K will have vPC peer between them. Each 4 N2K will connect with redundant uplink via vPC with this N5K. N5K will run Eigrp routing and will be the gateway of this new DC server.

WAN between DC1 & DC2: DC1 VSS will connect with DC 2XN5K with 2X10G links. we want to do MEC at VSS side and L3 vPC at DC2 side.

If we have VSS at both end it might not be a problem. Both the link will work together as 20G aggregated link. But as we are using N5K at one end, so it creates a confusion whether it will work properly is this scenerio or not. This is my 1st question.

Also I would like to know,
1) In VSS I have configured 1 VLAN interface for server gateway. But in N5K do I have to configure at 2 switch seperately?
2) In WAN routing VSS shows as 1 device. Does this 2 N5K will show as 2 seperate hops or L3 vPC will allow them to act as a single device while traceroute from one end to another end.

I am not sure if my questiones are so elementary level or not. As I am very new to this technology I would like you all to get me some suggestions or documention or links regarding this design. I am also attaching the diagram.

Answer:

You solution in step 1-3 are fine. I will use the same solution based on the following:
1. VSS is a logical switch, in the N5K's perspective, it is 1 switch. You are acutally ECMP upstream, which is good. Just let routing protocol to take care the job.
2. The cross /30 link between N5K-1 and N5K-2 is used only if one uplink failed. Please note that the L3 /30 cross link is not part of vPC peer-link. It is a dedicated interface. Please see the below diagram.
In term of HSRP, you have to understand one thing first. In vPC, HSRP behavior has modified, both switch will forward traffic (different from C6K where only one is active). Please see the below link on how HSRP works under vPC (somehow this link is broken right now, let me see if I can get someone to fix it):

http://www.cisco.com/en/US/prod/collateral/switches/ps9441/ps9402/white_paper_c11-516396.html

To answer your question:
1. When N5K-1 goes down, N5K-2 will forward traffic out, and vise versa.
2. When vPC peer-link goes down. vPC secondary will shut down all vPC related interfaces and SVI. If SVI is down,Cisco 3945 routing protocol will stop the advertisement. Original comes from

http://www.kerchoonz.com/account/submit/add-blog/added_309996/