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VXLAN and multicast

zshowip
Enthusiast
Enthusiast

Hi, As we know vxlan needs multicast config. If using broadcast instead of multicast, what would happen? thanks

1 Accepted Solution

Accepted Solutions

You can not use Broadcast !!! Yes you can not why ? because we run VXLAN over L3 underlay and L3 underlay can not accept broadcast (L3 behave) but it accept multicast. 
so we broadcast over L3 multicast. 

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7 Replies 7

You can not use Broadcast !!! Yes you can not why ? because we run VXLAN over L3 underlay and L3 underlay can not accept broadcast (L3 behave) but it accept multicast. 
so we broadcast over L3 multicast. 

zshowip
Enthusiast
Enthusiast

Thanks for your reply. 

"L3 underlay can not accept broadcast (L3 behave) but it accept multicast.  .." 

Its because L3 underlayer would get mess with broadcast, or something else? 

router by default will not forward broadcast traffic. 
as you know the router not like SW forward broadcast. 

VXLAN+Underlay+-+Multicast.jpg

zshowip
Enthusiast
Enthusiast

Right, so each VTEP communicate each other via multicast. and can we say VXLAN is used only on ACI? if so, there should be some table in leaf and spine to allow us to check their status, right? 

Yes each other connect via multicast.

zshowip
Enthusiast
Enthusiast

Thank you!

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