vPC to vPC between 2 Pairs of N7K's

[Henry Rehne]

We have a pair of N7K distribution switches connected to a pair of N7K Aggregation switches.

We run vPC on both pairs of n7k's.

n7k-d1 has two interfaces in a Port-Channel connecting to n7k-a1 & n7k-a2. (PC1)

n7k-d2 also has two interfaces in a Port-Channel connecting to n7k-a1 & n7k-a2. (PC2)

My problem is that Spanning-Tree is blocking PC2 and all traffic from n7k-d2 is traversing the Peer-Link before reaching the Aggregation layer.

Can anyone tell me if this is the best design for connecting two pairs of n7k's with vPC or if a better design would be to connect all 4 links into the same Port-Channel and vPC?

[sean_evershed]

Hi,

Check out this document on single-sided vs double-sided vpc.

https://supportforums.cisco.com/docs/DOC-20836

Don't forget to rate all posts that are helpful.

[Henry Rehne]

Thanks.

I see this option is for n7k to n5k.

Is this option also available for n7k to n7k and is this a Cisco Best Practice recommendation?

[sean_evershed · Accepted solution]

Hi,

The same principles apply since both a N7K and a N5K run Nexus OS.Therefore they both support vPC.

That document that I referred you to was written by a Cisco employee.

See also this Cisco best practice document for double sided VPC:

http://www.cisco.com/en/US/prod/collateral/switches/ps9441/ps9670/C07-572834-00_STDG_NX-OS_vPC_DG.pdf

My guess is that both docs shows a N7K connecting to a N5K since deploying multiple N7K's in a data centre is very expensive unless you have a good business case. Rather most organisations choose to deploy the cheaper architecture of a N7K connecting to a N5K. Hence this cheaper option is discussed.

Hope that helps.

Cheers

Sean

[Henry Rehne]

Thanks Sean.

We have the Duoble-sided vPC concept between the N7k Distributions and the N5k Access switches.

Just need to verify that we can run the same between the Aggregate and Distribution.

I know the N5k's had some Caveats around the connectivity from the Servers regarding dual-homing.

Need some confirmation that similar Caveats don't exist with this design.

[Oleksandr Nesterov · Accepted solution]

Hi Henry

Same back-to-back vpc design is supported between pairs of n7k and n5k devices. There shouldn't be any issues.

HTH,

Alex

[Henry Rehne]

Thanks Guys.

Had a Chat with our Cisco Rep and he also agrees that the Double-Sided vPC is the correct design between our n7K Core and n7K Distribution switches.

[Oleksandr Nesterov · Accepted solution]

Hi Henry

Happy that you have found answers to your questions.

Regards,

Alex