Wireless Access

Contributor II

Big Broadcast domain.


  Finally, we are upgrading the LAN and we are going to use 3800 series Aruba switches. My question would be what is the downside of having a single big broadcast domain, let's say /17 for example. Some of the team members are not comfortable with big broadcast domain. Any input from the pros would be appreciated. 


Re: Big Broadcast domain.

Keep it small as needed makes troubleshooting more easy. All broadcast traffic (and in some cases also multicast traffic without snooping) will floods to all clients.

Possible l2 issue could be very hard to troubleshoot in big broadcast domains.

Keep it small as you can, /24 /23 or max. /22 in most cases.
Kind Regards Marcel Koedijk
HPE ASE Flexnetwork | ACMP | ACCP | Ekahau ECSE Design - Was this post usefull, Kudos are welcome.
MVP Guru

Re: Big Broadcast domain.

As your question is posted in the Wireless forum, it's not fully clear if you refer to wired or wireless clients in your question.


If you connect a controller (that does broadcast filtering/conversion) with many wireless clients, you should, in general, take the subnet as large as possible. Check the Single VLAN Architecture for WLAN VRD for more information and backgrounds.


In a pure-wired environment, I agree keeping the broadcast domains small (just a hundred or few hundred devices per VLAN) is considered best-practice for the reasons mentioned in the previous answer.

If you have urgent issues, please contact your Aruba partner or Aruba TAC (click for contact details).
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