topic Re: SDN - L2 vs L3 in Software-Defined Access (SD-Access)

SDN - L2 vs L3

Kalimoz — Thu, 26 Jan 2023 15:30:56 GMT

Is it possible to build and SDN topology and still keep running a L2 environment?

Or L2 is definitely "killed"?

Re: SDN - L2 vs L3

Scott Hodgdon — Thu, 26 Jan 2023 15:40:17 GMT

Cisco SD-Access is made up of an underlay (transport) and overlay (services). The underlay is Layer 3 with no Layer 2 option, but the overlay can deliver both Layer 2 and Layer 3 services.

There are many SD-Access customers that use this Layer 2 option in the overlay.

Cheers,
Scott Hodgdon

Senior Technical Marketing Engineer

Enterprise Networking and Cloud Group

Re: SDN - L2 vs L3

Pascal Lacroix — Fri, 17 Mar 2023 13:54:23 GMT

Hi Scott,

what do you mean with this Layer 2 option in the overlay?

kind regards,

Pascal

Re: SDN - L2 vs L3

jedolphi — Sun, 19 Mar 2023 23:28:39 GMT

Hello Pascal, Scott is saying that in the SD-Access overlay there's a range of L3/L2 configuration options: 1. An Anycast Gateway for routing (L3) + an L2VN for east/west switching (L2), or 2. An Anycast Gateway for routing (L3) with no east/west switching between Fabric Edge Nodes, or 3. An L2VN (think of this as a giant VLAN stretched accross the SD-Access Fabric) with no Anycast Gateway.

#1 and #2 have the IP gateway in the SD-Access Fabric, #3 relies on an IP gateway outside the SD-Access Fabric. I explained this at a very high level in BRKENS-2810 -> https://www.ciscolive.com/on-demand/on-demand-library.html?search=brkens-2810&search.event=1675713481674001JK6C#/session/1675722367640001tGRb

Please note that #3 is effectively a big VLAN and as such it comes with all the scaling problems of VLANs, so only use it if you must, and be cognizant of BUM flooding