Why multicast is required in SD-Access

[Majed Saeed]

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

[balaji.bandi]

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

[M02@rt37]

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

[Flavio Miranda]

@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