topic SD Access underlay multicast in Software-Defined Access (SD-Access)

SD Access underlay multicast

KevinR99 — Tue, 27 Jan 2026 16:35:37 GMT

I have multiple fabric sites and I want a shared underlay multicast tree across them. Currently they have been configured as standalone multicast topologies because each site points to its own Borders as the PIM RP in the underlay. There is no workflow in Catalyst Center for the underlay multicast. Only for overlay VN's which run over the underlay multicast.

So my question is what is the best/easiest way to merge the various fabric underlay multicast topologies.

Site A is the main site and it has 2 Borders acting as Anycast RPs using MSDP between them. When I look at that site the Edge devices all statically point to this Anycast RP address with # ip pim rp-address x.x.x.x

On other sites they have their own site specific RP. I can easily change that on the other site Borders by changing the RP command. However, I also have many Edge devices that would need changed. What is the best way to merge these underlay multicast configs such that they all point to site A's Anycast RP address?

Thanks, Kev,

Re: SD Access underlay multicast

M02@rt37 — Tue, 27 Jan 2026 16:49:18 GMT

Hello @KevinR99

You want sources at remote sites to also register with the site A RP ?

Re: SD Access underlay multicast

balaji.bandi — Tue, 27 Jan 2026 17:36:54 GMT

check below suggestions :

https://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst9300/software/release/17-9/configuration_guide/lisp_vxlan/b-179-lisp-vxlan-fabric-cg/multicast-lisp-vxlan.html#lisp-vxlan-fabric-multicast-overview

Re: SD Access underlay multicast

Andrii Oliinyk — Tue, 27 Jan 2026 19:14:45 GMT

until Cisco will automate it with CatC i think most scalable way to do it is to leverage inter-domain multicast routing by developing & deploying on BNs network templates with MSDP bw them :0D

Re: SD Access underlay multicast

Cristian Matei — Sun, 01 Feb 2026 16:22:11 GMT

Hi,

@KevinR99 How many multiple sources, how many multicast receivers and how many multicast groups do you have? Do you have multicast receivers in both sites (if in multiple sites, how many sites), do you have multicast senders in both sites (if in multiple sites, how many sites)?

The above info is needed to find best solution.

Thanks,

Cristian.