Nexus 5k to 2K design

[dejian007]

Hi All,

I need some help with suggestions for a design to connect Nexus 5600 to Fex 2k. Currently there is a stack of cisco 3800 that will be replaced by the new 5k with Fex. The servers are single homed with 1G uplinks with future plans to bring in dual homed 10G capable servers.

We have nexus 5672 which will be running VPC and Fex 2348. The current uplink from the 3850 stack is 10G. I have setup a design for the setup but want help with over subscription issues for future.

Also I need some recommendations on which ports to use for uplinks on the FEX and for VPC peer links between the 5K. I have attached a sample design diagram. I would really appreciate if someone can post some thoughts if the design is alright and future proof.

As there are just 6 QSFP ports on the 5k and the Fex, I am not sure if using 2 QSFP for peer link is the right idea?

[Yannick Vranckx]

Hi,

Any reason you want to dual home those FEX to the 5K. As an experience i have come to the realisation that adding that layer of connectvity will just add up the complexity of the network instead of more redundancy.

I would single home your FEX to the 5K, you can still dual home the host to the FEX'es and build a vPC. 

Why did i choose the single home?

- ISSU on dual home scenario (Enhanced vPC) is very limited to non existing, all of your FEX'es are known on both 5K. So an upgrade would require a downtime from all of the FEX'es

- This layer of redudancy is adding more complexity to the network but not more redundancy in my opinion. Your host will remain dual homed to the FEX'es.

- In eVPC, the vPC's are automatically created if i remember correctly, i did not like this. Configuration wise it added a bit more confusion then just copy pasting the same config on both 5K's.

- Using switch profiles to sync config i found to be very annoying.

[Rick1776]

I concur with all the statements as well. 

Straight-through is the better design and was easier for the configuration. Also as stated before config-sync is kind of a joke. Your better off building the config then copy and paste into the second switch.

This is a pretty good link for the configurations your looking at.

https://www.cisco.com/c/dam/en/us/products/collateral/switches/nexus-5000-series-switches/C07-572829-01_Design_N5K_N2K_vPC_DG.pdf