I want to add more notes to this weeks post that will help. See this post for the beginning of this install. So, my focus will be primarily on the connection of the 5000s to the core switches. In this case, I happened to be connecting my two 5000s to two 6500s for redundancy.
It is really important that you make the all port-channels to the core a part of the same 'port-channel number'. For example, 'interface port-channel 5'. Here is a drawing that the TAC guy drew up for me.
So, if you will notice, there are a few numbers in this drawing. I had on N5K-1 a vPC of 11. On N5K-2, I had a vPC of 11. But on the core switch, we had a 'interface port-channel 25' going to N5K-1. Again, on the core, we had 'interface port-channel 26' to N5K-2. Well, as it turns out, this doesn't work well, according to Cisco TAC, and I believe it. I didnt know this until today, but from what I was seeing, it didn't seem stable. Also, even though there is no real vPC configuration on the core (except the port-channels and interface commands), TAC recommends that the port-channel interfaces match the port-channel interface numbers of the N5Ks. When I did this, things got stable and I didn't have any issues afterwards. If you will notice in the above drawing, there is a vPC circle above 'core1'. That is what it is 'supposed' to be. Port-channel 11 for N5K-1, port-channel 11 for N5K-2, and port-channel 11 for core1.
If you are going to a second core 6500 like I was, use a different port-channel number for the N5K-1, N5k-2, and the second 6500. I used port-channel 15.
Test your connections. I put my laptop up on one of the 2232s and pulled the power from N5K-1. Ping still works to the core. I powered up the N5K-1, let the FEXs register, and pulled the power to N5K-2. Pings still gets to core. Power N5K-2 back up. Do the same for the second FEX. Redundancy confirmed works.
Im adding these links below as an afterthought to this series. This Nexus install was a four part series, this link being part two. Here are the links to the others if you are interested.
For the notes on the install of the 5000s/2000s and how to configure a redundant setup, click here.For the notes on the "FEXs", click here.
For some config examples without explanations, click here.