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]> 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]] *On Behalf Of *Brian Helman > *Sent:* Monday, July 25, 2016 10:22 AM > *To:* [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 > <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/.
