Use two vpc peer-link in Cisco N9K

[johnlloyd_13]

hi,

is it possible to configure two vpc peer-link (port-channel trunk) between two N9K?

i.e. port-channel 1 would be a temporary trunk and uses MM fiber cable and port-channel 2 would be the 40GBASE-CR4 pre-fab direct cable.

the 40GBASE-CR4 would arrive in a later date that's why i need to build the temporary vpc-peer link via port-channel MMF.

or do i need to remove/decom port-channel 1 (MMF) before i configure the "permanent" 40GBASE-CR4 port-channel 2?

or can i do this in parallel?

[MHM Cisco World]

NSK vPC have only one peer-link it can not have two parallel peer-link.

MHM

[DanielP211]

Hello!

Vpc peer-link can be only one. So you will need to reconfigure when the 40G becomes available, it won't work parallel. 

BR

[johnlloyd_13]

hi,

would this be a simple 'no vpc peer-link' on the old po1 trunk and add 'vpc peer-link in the new po2?

interface port-channel1   <<< MMF
description ### TEMP TRUNK ###
switchport
switchport mode trunk
spanning-tree port type network
no vpc peer-link

-----

interface port-channel2   <<< 40GBASE-CR4 direct cable
switchport
switchport mode trunk
spanning-tree port type network
vpc peer-link

[MHM Cisco World]

Do this step in maintenance window

The secondary vPC will shut down the SVI and not forward traffic to vPC member if it detect peer-link down

Be careful friend 

MHM

[balaji.bandi]

before you proceed to remove any link understand the failure scenario and make necessary action.

https://community.cisco.com/t5/data-center-and-cloud-knowledge-base/vpc-failover-scenarios-and-troubleshooting-checklist/ta-p/3143104

If all the end devices are dual homed, bring down the secondary device offline and connect new VPC link config on both and bring up VPC link and Keep alive link and Service port is good approach. rather full blown failures.

[johnlloyd_13]

hi balaji,

i don't think i need to make secondary N9K offline/power off. the N9K would still be an isolated switch pair, not included in the STP L2 switch fabric, and no cables swing to these yet, i.e. trunk cables to access switch and downstream devices (FW, server, router, etc).

just to confirm, i pre-patch the 40GBASE-CR4 direct cable, configure po2 trunk interface.

then shutdown old po1 on both N9K, do a 'no vpc peer-link' under po1, configure 'vpc peer-link' in the new po2?

[MHM Cisco World]

We dont say your way of changing peer-link is wrong' what we suggest is do in window' 

Peer-link is down can lead to blackhole and traffic is drop' because the SW connect to both NSK (vPC) will not notice of peer-link down' so we suggest safety do change of peer-link.

MHM

[balaji.bandi]

As i understand this is not put in live and no live services, then you can do what ever order it does not matter.

[johnlloyd_13]

hi balaji,

yes, the N9K pair isn't in production yet.

i'm just going to prepare/dump the config from old core switch to N9K.

so the 'vpc peer-link' will not be an issue/downtime while i'm preparing the new N9K.

there's just a delay to deliver the special cable 40GBASE-CR4.

[MHM Cisco World]

your way is correct But as I mention before you need to do it in window if these device in production

this lab 
two PO between two NSK 
one use as Peer-link other no 
then I remove the Peer-link from one and add it other PO 

notice I share the show spanning tree since there are two link between the NSK one of Link is BLK and I want to notice you that Peer-link ALWAYS must be FWD and it is in my lab 

MHM