SDN Questions

[Sascha2020]

Hey guys, 

currently i'm struggling to find answers to the following questions, maybe you could help me?

1. Is it possible to implement a SDN-Solution which works with the protocols OSPF, IS-IS or EIGRP?

2. Currently we got a 3-Tier-Architecture and our Access Layer is connected to the Distribution over Layer-2 only so routing first happens at the Distribution Switches. So when we would set up SDN, has the routing go till the Access Switches at Layer 2 or could it be left like it currently is?

3. Is it necessary to switch to a Spine-Leaf-Architecture in order to implement a Cisco SDN-Solution, or would it be possible to still use the mentioned 3-Tier-Architecture with an SDN-Solution? 

Notice: Almost only hardware from cisco in network

Thanks in advance for your help and please excuse my bad english.

Best regards

Sascha

[inderdeeps · Accepted solution]

Yes SDN solution is basically running overlay tunnels over the underlay protocols like OSPF, ISIS or EIGRP, So they are very much work with these protocols.

If you are talking about the Campus environment and if your aproach is towards SD-Access Fabric the solution can be 2-tier ( Access node and Border Node) or 3 tier ( Access, Distribution and Border Node). For SDA solution you can use any vendor for distribution layer but Access and Border node should be Cisco and the recommended devices as per the guidelines. Here also the concept is based on the Overlay protocols like LISP ( For location identifier) and VXLAN. The segmentation is not with the VLANs now, its with the SGTs managed by Cisco ISE. Go with the below link you will get to know

https://www.thenetworkdna.com/2020/09/cisco-sd-access-architecture-control.html
https://www.cisco.com/c/en/us/td/docs/solutions/CVD/Campus/cisco-sda-design-guide.html

Spine-Leaf architecture is a Datacenter solution and it depends upon how big your environment is to implement a 2-tier or 3-tier architecture. As to remove the complexity of the solution the Spine-leaf comes into picture over th traditional Nexus 3-tier architecture. So technically, Spine-leaf is a 2-tier architecture and is enough to maintain big environments. Check all Cisco ACI topics below to get more about it
https://www.thenetworkdna.com/search?q=ACI

Regards
Inderdeep Singh
www.thenetworkdna.com

[Sascha2020]

Hello Inderdeep Singh,

thank you very much for your informative reply!
So if i got that right, a cisco SDN-Solution, like SD-Access, implements an overlay-network on top of a existing underlay (Layer-3?) network. And in that overlay-network many different services and protocols in all different logical layers can be implemented. 

Are my assumptions correct so far?

And how is it prevented that this creates a bottleneck if all the implemented protocols and services in the overlay-network are limited to the specifications of the underlay-network? Like for example everything from the overlay-network still get encapsulated with IP-Protocol on Layer-3 in the underlay network?

please excuse my may stupid questions, the more i study online, the more confused i am.

Thanks in advance and best regards

Sascha