Migrating to New Nexus VPC, but No 1G/10G/25G ports

[TrivialPants]

Hi All,

I am installing a new Nexus VPC switch that uplinks from my core router. It will aggregate handoffs from a Bundle-ether interface. 

Currently the Nexus switch has different access ports that take untagged or trunked traffic based on different VLANs and put them into the correct VLAN, etc. 

The new switch will not have 1/10/25G ports. It only has 100G ports. 

I wanted to see if this was a good idea? Can I just uplink the old Nexus switch to the new switch, and keep it in VPC? 
I will put the new Nexus directly in line with the edge router as a bundle (with more members).

So I will be going from this:

[Edge router ] --> Bundle --> Old Nexus 1/Nexus 2 (vpc pair) 

to this:

[Edge Router] --> Bundle --> New Nexus1/Nexus2 (vpc pair) --> port-channel trunk-> Old Nexus1/Nexus2


Will this work?

[marce1000]

 - For VPC , the port capabilities (speed) have to match between the new and the old switch ,

 M.

[M02@rt37]

Hello @TrivialPants 

Your new nexus switches (New Nexus1/Nexus2) should be configured as a new VPC pair with their own VPC peer link and keepalive link. The existing Nexus VPC pair (Old Nexus1/Nexus2) should remain a separate VPC domain. You will be forming a "cascading VPC" where the old Nexus VPC pair is downstream from the new Nexus VPC pair. The old Nexus switches will have a port-channel (trunk) toward the new Nexus VPC pair, and this uplink should also be configured as a VPC on the old Nexus to maintain high availability and redundancy.

The edge router will now connect to both new Nexus switches via a larger bundle (with additional 100G members). 

Ensure all VLANs and STP configurations are correctly propagated between the new Nexus and old Nexus switches. Since the old Nexus switches will no longer directly uplink to the edge router, verify that they will still receive the necessary VLANs via the port-channel trunk to the new Nexus pair.

[TrivialPants]

Thank you when we are configuring the VPC on the old & new, do we need to use a different /30 IP for the new & old VPC keep alive and domain #? Or is that all local to each switch? 

Example: 

VPC pair 2  has this VPC config:
vpc domain 1
role priority 30
peer-keepalive destination 172.31.1.1 source 172.31.1.2 vrf default

interface Vlan3967
no shutdown
ip address 172.31.1.2/30


(same thing but mirrored on the other member of VPC pair). 

Should we choose a different VLAN to set up the VPC in as well as a different VPC #? Or will that matter?

[M02@rt37 · Accepted solution]

Hello @TrivialPants 

Each vPC domain id must be unique within the same L2 domain to avoid issues with consistency checks and vPC orphan port beahviour.

As concerned the vpc keepalive link, while it can technicaly use any routed path, it is a best practice to isolate it using separate VLAN and IP subnets for clarify TBSHOOT.

[TrivialPants]

Okay perfect! This helps a bunch! I will use VPC domain 2 for the new switch with a different keep alive /30 IP address on a different VRF. 

the existing VPC, I will use the existing link and VLAN as well as just VPC domain 1.

[vishalbhandari]

@TrivialPants Yes, your plan should work. Uplinking the old Nexus switches to the new Nexus vPC pair via a port-channel trunk is a common design. Just ensure that the vPC configurations (peer-link, peer-keepalive, and consistency parameters) are properly set up between the new Nexus switches. Also, verify VLAN consistency across the vPC domain and port channels. Since the new switches only have 100G ports, make sure the old switches can support compatible breakout or adapter options if needed. Overall, this design improves scalability while maintaining redundancy.