Actually, you reduce the broadcast traffic with smaller subnets. Remember that all clients on the subnet *must* respond to a broadcast.
Smaller subnets generally mean fewer clients responding to a given broadcast. This leaves more airtime for productive Wi-Fi traffic. Bruce Osborne Wireless Engineer IT Network Services - Wireless (434) 592-4229 LIBERTY UNIVERSITY Training Champions for Christ since 1971 From: Jake Snyder [mailto:[email protected]] Sent: Monday, July 25, 2016 1:28 PM Subject: Re: How big are your wireless segments? One thing to remember is that over the air you have the same amount of broadcast whether it is one vlan or a pool of 4. For Example: If you have 4 client segments that are a /24, and each AP has a client on one of the 4 subnets, you still send the sum of 4x /24 network broadcast over the air. Meaning only on lightly loaded APs where you don't have all 4 subuets do you get a net gain of airtime. Same applies for link-local multicast. Smaller subnets in pools don't really gain you much without the suppression techniques, and with the suppression techniques, you don't need the smaller subnets. The place where pools/groups of vlans are attractive is where you may be using public IPs and don't have a large contiguous block of IPs in which to place clients. So picking 4 non-contiguous /24 networks is easier to do than picking a full class B. On Mon, Jul 25, 2016 at 11:04 AM, Tim Tyler <[email protected]<mailto:[email protected]>> wrote: Brian, We have pools of /22 /23/ and /24. We separate our pools from students vs fac/staff (still on the same ssid). It may be ok to do /16. I know that Aruba does a lot to prevent broadcast storms, but I feared the overhead of one large segment might have on it. We also give students a different ip pool depending whether they are in a residential building vs an academic/admin building. This allows us to shape traffic differently. But this will become less of an issue as we acquire more bandwidth (hopefully). I am curious of those using /16, does that resolve your layer 2 issues? Aruba does a good job of bridging many layer 2 solutions anyways, but having one /16 vlan does seem enticing and perhaps unnecessary for bridging protocols. However, I am curious about other overhead efficiency issues. Tim From: The EDUCAUSE Wireless Issues Constituent Group Listserv [mailto:[email protected]<mailto:[email protected]>] On Behalf Of Brian Helman Sent: Monday, July 25, 2016 10:22 AM To: [email protected]<mailto:[email protected]> Subject: [WIRELESS-LAN] How big are your wireless segments? We are in the process of moving from a controllerless vendor to Aruba. Our current design is very segmented, to keep wireless device broadcasts from overwhelming the network and AP’s (we had this problem back in 11g days). Presently, we’ve limited segments to /23’s (give or take). In your controller-based environments, how large have you let these segments go? Is a /21, /20 … viable? -Brian ____________________________________ Brian Helman, M.Ed | Director, ITS/Networking Services | •: 978.542.7272<tel:978.542.7272> Salem State University, 352 Lafayette St., Salem Massachusetts 01970 GPS: 42.502129, -70.894779 ********** Participation and subscription information for this EDUCAUSE Constituent Group discussion list can be found at http://www.educause.edu/groups/. ********** Participation and subscription information for this EDUCAUSE Constituent Group discussion list can be found at http://www.educause.edu/groups/. ********** Participation and subscription information for this EDUCAUSE Constituent Group discussion list can be found at http://www.educause.edu/groups/. ********** Participation and subscription information for this EDUCAUSE Constituent Group discussion list can be found at http://www.educause.edu/groups/.
