Quick vPC Question

[visitor68]

Need my thinking verified...

If I dual home a device directly into 2 5000 switches in a vpc cluster, I can run active active LAG uplinks, right? But how about if I have that same device uplinked to 2 FEXs which are then uplinked to the same 2 5000 switches in a vpc? Can you still enjoy the functionality of vPC between the 5000s even if youre not directly connected to them? Can you still run act/act LAGs up to the FEXs?

Thanks

[vinod rathore]

Thanks Paul for explanation,

I understand that end switch doesn't require any VPC command configuration and just need simple port channel config, that's it.

"Marwan's last diagram is a supported configuration under current code."

means the N55K N56K and N6K supports eVPC at present whereas N7K doesn't support this till now.

[vinod rathore]

Hello Marwan,

I really apologies if my question seems to be weird.

As per my knowledge in above diagram both the server A & B will be part of VPC domain 20.

Going forward any device added to network having connections to both N5Ks like switch (in middle of both server) will be part of VPC domain 20 ? or is there any case where in switch can be configured as it can be part of VPC domain 10 ?

If yes in that case will it be eVPC scenario for N7Ks and switch perspectives ? 

[Paul Chapman]

Hi Vinod -

It is only eVPC when you are creating a port-channel from a dual homed N2K.  In the case of this diagram, the servers and downstream switches are connected by a standard vPC.  As far as the downstream devices are concerned, they are connected to a single upstream switch.

The connection between the N7Ks and the N5Ks is called a double-sided or back-to-back vPC.

To be clear, the downstream devices have no idea about vPC domains.  The domain is created on the Nexus switches so that they can establish a peer relationship and act as a single virtual switch to the downstream devices.  When we put 2 unique vPC pairs together we must ensure that their domain numbers are different so that they do not confuse each other in a direct connection scenario like the one shown in the diagram.

HTH

PSC

[vinod rathore]

It is only eVPC when you are creating a port-channel from a dual homed N2K.

Do you mean two N2K dual homed to upstream N5K peer with VPC configuration and then any server dual homed to upstream N2Ks is only eVPC valid scenario.

In above diagram there is no N2K instead N5Ks are dual homed to upstream N7Ks

is this not the valid eVPC scenario ? 

[Paul Chapman]

Hi Vinod -

That is correct, that diagram does not show eVPC.  Here's a quick sketch I put together showing different types of port-channels.

Since we can consider the N2Ks as external line cards we can include them as part of the vPC domain.  For the N7Ks the vPC to SRV1 would be the same with or without the FEX.  For SRV2, it is an eVPC since it is connected to dual homed FEXs.

Hope that clarifies.

PSC

[vinod rathore]

Thanks Paul, it put clear visibility now.