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VXLAN/EVPN Multi-Site as OTV Replacement

I've got some use cases where I'd like to use something like OTV, but on Nexus 9Ks. Say two datacenters where each datacenter / site is 2 spine and 4 to 6 leaf switches, and only a few VLANs. I see little point to running VXLAN/EVPN within such small sites, just VPC and VLANs with SVI's on the core / spine switches. 

 

VXLAN/EVPN Multi-Site with pseudo-Border GW looks like just the approach I want. However, the use case focuses on migration, where's I'm more interested in a non-VXLAN new N9K based site operating "in legacy mode". 

 

Question #1: The documentation I've seen is a bit unclear, it says something about SVI's and trunks are not supported for external entities. I'd maybe add the word "**routing**" to that -- external entities that would want dynamic routing? I'd hope trunks and SVI's would be supported for internal clients, i.e. servers and other devices that are connected within a VLAN.  Seeing as that's how the "legacy" network would be operating, and the description about putting the anycast GW on the border GW. What exactly IS the caveat here? 

 

Question #2: With OTV, one only transports selected VLANs between datacenters. With the Multi-Site writeup, there is no discussion of VLANs that are *not* associated with VNI's, etc., mixed into the same VRF as the VNI-backed VLANs. Questions come to mind, like does routing between the two types of VLAN work, etc.? I built a small VIRL model (not multi-site per se, since the available Nexus image is not quite new enough) and routing between non-VNI and VNI-backed VLANs works fine, locally or over the overlay. I did have to put network statements into the VRF section of BGP for the non-VNI-backed VLANs. What is / is not supported in basic VXLAN/EVPN or Multi-Site along these lines? 

 

I should note that associating non-extended VLANs with unique VNI's appears to be one way of dodging this whole discussion. Might that be a Best Practice? (Makes the configurations more uniform...). 

 

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Re: VXLAN/EVPN Multi-Site as OTV Replacement

Question #1:

what do you mean with external entites? outside connetions? and you can use SVI for external connection and depending o your diagram you can have Dynamic or static routing and for example use the SVI for a PBR like configuration to send the data over one link or the other.

you can use the dynamic routing for the external conection just remember that if you want to send the VNI sements out of the VxLAN you have to redistribute them with match route-type internal on the IGP:

!

ip prefix-list TRAFICO_VXLAN_LANs seq 5 permit 192.168.1.0/24
ip prefix-list TRAFICO_VXLAN_LANs seq 10 permit 192.168.2.0/24

!

route-map RM-TRAFICO_VXLAN_LANs permit 10
match ip address prefix-list TRAFICO_VXLAN_LANs
match route-type internal

!

 

Question #2:

 two types of VLAN work?

Yes you can have the same vlan on both sides and with the anycast-routing enable you should be able to do this with no problem.

 

I recommend you tu use the Nexus 9Kv and virtualize the enviroment for this in my lab i have 2 DC one with 2 Spines and 4 Leaf and the other one with 1 Spine 2 leaf.

 

Saludos,

Gerardo Andree Mejia

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