This is what we've been doing for years (except we're using /22s). The issue
that we see now is that with near 100% wireless coverage on our main campus,
there are no dead spots or bad roaming areas. Users authenticate in on area and
move to the next area. Take the following scenario:
100 students attend a lecture in building "A". 25 of these students
authenticated to wireless on the east side of campus on controller 1 (they
received an IP in the range assigned that controller). Another 25 of those
students authenticated on the north side of campus on controller 2, 25 more on
the south side on controller 3, etc. Now, as they all walk to their lecture,
their wireless session roams until they sit down in the theatre. At this point
the APs in the lecture theare are servicing 4 separate networks (on the same
SSID). To me, it's really a moot point to discuss the wasted airtime of
management frames, broadcast, etc. Functionally speaking, all of the users are
sharing the radio spectrum as if they were on the same IP subnet. Even though
the students can only "see" the broadcast frames of their own network, they
still have to wait for the air to be clear.
This scenario is something we see all across the board in all areas of our
campus. So, as we don't have any VLAN pooling features and have to balance our
IPs manually so that none of the controllers "run out of IPs", my thinking is
why not just make it easier on ourselves and move to /21s and save the hassle
of balancing?
Regards,
Craig
SFU SIMON FRASER UNIVERSITY
Network Services
Craig Simons
Network and Systems Administrator
Phone: 778-782-8036
Cell: 604-649-7977
Email: [email protected]
Twitter: simonscraig
----- Original Message -----
From: "Kees Pronk" <[email protected]>
To: [email protected]
Sent: Wednesday, 1 August, 2012 23:05:49
Subject: [WIRELESS-LAN] Betr.: Re: [WIRELESS-LAN] Wireless Client Subnet sizing
Aruba networks advises to keep the subnets /23 (for big campuses) because of
wasted airtime due to increased management (beacons and mgt frames).
I agree Cisco has excellent technical content, but imho for WLAN specifically,
Aruba is better.
http://www.arubanetworks.com/wp-content/uploads/DG_HighDensity_VRD.pdf
Regards, Kees Pronk
Netwerk admin & engineer
Avans University of Applied Sciences
Diensteenheid ICT en Facilitaire Dienst (DIF) - ICT-Beheer
Bezoekadres:
Hogeschoollaan 1, Kamer HG204
4818 CR Breda, The Netherlands
Postadres:
Postbus 90116
4800 RA Breda
E: [email protected]
T: @rovinguser
>>> Tristan Rhodes <[email protected]> 8/1/2012 11:12 >>>
Like it was mentioned by Anders, this excellent material is freely available
after a registration. Funny though, it seems that you can access the file
directly:
Design and Deployment of Enterprise WLANs (BRKEWN-2010)
http://d2zmdbbm9feqrf.cloudfront.net/2012/usa/pdf/BRKEWN-2010.pdf
Cisco has the most technical content available, compared to any other network
vendor that I am aware of.
Cheers!
Tristan
--
Tristan Rhodes
Network Engineer
Weber State University
(801) 626-8549
>>> On 7/31/2012 at 5:01 PM, in message
>>> <CAP8VL9hbfk669TT=XGMu5WdMt25_eopDZ=xvcvceohabjrr...@mail.gmail.com>, Mark
>>> Duling <[email protected]> wrote:
Luke, it looks like that presentation isn't public. Can you say more about
Cisco's recommendations on that? Or are they simply saying /21 is the maximum
recommended size? I'd also be interested in anything they said about mcast as
it relates to size.
I've setup vlan select on a test WLAN with the intent of breaking up my /21
into smaller pieces for the fall, but I've had no problems with it (though
mcast is off). But I thought I would use smaller subnets since our wireless use
has gone up quite a bit in recent years and doing it is so simple to do now.
I've heard conflicting info, and to my surprise one time a TAC engineer
suggested they should be no larger than /24, which I think is erroneous.
Mark
On Tue, Jul 31, 2012 at 2:43 PM, Luke Jenkins <[email protected]> wrote:
What type of gear are you using?
Cisco is now recommending using /21s for their unified wireless gear (Sujit
Ghosh, Cisco Live US 2012 BRKEWN-2010, Slide 75).
-Luke
=-=-=-=-=-=-=-=-=-=-=-=
Luke Jenkins
Network Engineer
Weber State University
On Jul 31, 2012, at 11:59 AM, Craig Simons <[email protected]> wrote:
> All,
>
> We are looking at re-engineering our wireless networking IP space and I'm
> wondering what type of boundaries other have pushed their networks to. We are
> currently using /22 networks (14 of them) most of which during a busy period
> of the day will run around 75-80% utilization (at least as far as DHCP
> assignments go). When I look at most APs during the day, I see that most APs
> have users belonging to several networks (roaming), and as we have multicast
> disabled, it would seem that the advantages of segregating wireless networks
> on the basis of limiting broadcast domain are moot. Is anyone running /21
> networks or larger?
>
> We've investigated NAT, but accurately logging internal-external IP address
> assignments for our users has proven difficult. Our vendor also doesn't
> currently support any type of "VLAN pooling" feature.
>
> Interested in your opinions,
> Craig
>
>
>
> --------------------------------------
> Craig Simons
> Network Operations
> Simon Fraser University
> Burnaby BC, Canada
> em. [email protected]
> ph. 778-782-8036 ( tel:778-782-8036 )
> ce. 604-649-7977 ( tel:604-649-7977 )
> tw. twitter.com/simonscraig
> --------------------------------------
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