Spine and Leaf design - what do you do for redundant TOR switches

[carl.townshend]

Hi guys

Most of our networks use Cat 9K switches, for servers etc we will normally have 2 9300 switches in a stack, and each server as a link to each TOR switch for redundancy.

How is this achieved in a Spine and Leaf ACI network, would you just put 2 leafs in the rack? would these leafs be directly connected to each other or not? or can you stack leaf switches ?

If 2 leafs in a rack and a server in the same rack needs to talk to another in the same rack, but each servers active port is on the separate leaf, would this traffic need to go to the spine and back if not directly connected?

Cheers

[M02@rt37]

Hello @carl.townshend 

Server attached on different LEAF (say ServerA on LEAFA and ServerB on LEAFB), the flow will always do LEAFA-SPINE-LEAFB.

Best way is to attach each server on a rack on LEAF co localized in the same rack. In this context, Vm on each server in the same rack => the Flow "stay" in this rack !

You could have 2 Leaf on a rack, these Leaf should be attached to each SPINE. Not necessary to stack them. AS concerned LEAF base on NX-OS, not mandatory to configure vPC between LEAF....depends of your requirements....ESI Multihoming could be a solution.

[carl.townshend]

Hi there

So what if we wanted to create etherchannel between 2 leaf switches for the VMware? would you need to create VPC between the leaf switches? is this normal practice ?

Same as in the link here

Understand and Configure Nexus 9000 vPC with Best Practices - Cisco

If not etherchannel/vpc then how would it work ?

cheers

[M02@rt37 · Accepted solution]

Hello @carl.townshend 

You should use ESI multihoming. No need of vPC between two Leaf. 

https://www.cisco.com/c/en/us/td/docs/switches/datacenter/nexus9000/sw/7-x/vxlan/configuration/guide/b_Cisco_Nexus_9000_Series_NX-OS_VXLAN_Configuration_Guide_7x/b_Cisco_Nexus_9000_Series_NX-OS_VXLAN_Configuration_Guide_7x_chapter_01010.html

https://nwktimes.blogspot.com/2019/05/evpn-esi-multihoming-part-i-evpn.html?m=1

[carl.townshend]

Hi

Can you still do VPC between spines?

Is the way you are proposing require ACI or can be done manually ?

[M02@rt37]

@carl.townshend 

what vPC between Spines ? No need of that. Each Spine to each leaf, each SPine acting as RR on the Overlay Control-Plane layer.

vPC between Leaf is possbile - but you have in charge the vPC domain configuration etc.... I prefer ESI multhihoming for my prupose of attached one Server to two Leaf in the same rack.