topic Re: Why multicast is required in SD-Access in Software-Defined Access (SD-Access)

Why multicast is required in SD-Access

Majed Saeed — Wed, 04 Feb 2026 10:58:48 GMT

Hi , May i ask Why multicast is required to operate SD-Access , in other word what happened if multicast wasn't enabled ??

Re: Why multicast is required in SD-Access

balaji.bandi — Wed, 04 Feb 2026 11:13:23 GMT

First, we need to ask about the requirement of Multicast in the network, in most cases, yes.

in SD-Access

Certain protocols—like ARP, DHCP, and mDNS—rely on "B-U-M" (Broadcast, Unknown Unicast, and Multicast) traffic to work

you can read more here :

https://community.cisco.com/t5/networking-knowledge-base/cisco-sd-access-layer2-flooding/ta-p/3943916#toc-hId--1906649608

https://www.ciscolive.com/c/dam/r/ciscolive/global-event/docs/2025/pdf/TACENT-2028.pdf

Re: Why multicast is required in SD-Access

M02@rt37 — Wed, 04 Feb 2026 11:16:44 GMT

Hello @Majed Saeed

Multicast is used as underlay to handle BUM traffic _ same as DC architecture Spine/Leaf.

See here informations => "Cisco SD-Access Multicast" chapter:

https://www.cisco.com/c/en/us/td/docs/cloud-systems-management/network-automation-and-management/catalyst-center/cisco-validated-solution-profiles/validated-profile-sda-deployment.html

Re: Why multicast is required in SD-Access

Flavio Miranda — Wed, 04 Feb 2026 11:36:40 GMT

@Majed Saeed

Multicast is required in SD-Access the same way it is required in any other technology. The basic principle is always the same.
In SD-Access, not only on the underlay, but also on the overlay, multicast is required and available by default "SDA Native Multicast"
If you want to deep dive on it, look documentation like

https://www.cisco.com/c/en/us/support/docs/cloud-systems-management/catalyst-center/222406-verify-native-multicast-in-sd-access-fab.html