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Large building wifi network, 2,000 wifi devices

Posted on 2011-09-20
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Last Modified: 2012-05-12
I have to set up a wifi network with about 2000 wireless devices.  I have the access points to do it, but should i setup dhcp on the ap's or should i setup a dhcp server to handle the ip's?  It is only for internet browsing and nothing else.  The building will provide me the bandwidth but not the ip's to support 2000 wifi clients.  i would plan for at least 2500 ip.  I was thinkg of setting up a 2003 server with Dhcp on it
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Question by:kabrutus
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16 Comments
 
LVL 22

Expert Comment

by:eeRoot
ID: 36571501
You'll have an easier time managing this network if the DHCP is centralized.  You can use a Windows server, a layer 2.5 switch, a layer 3 switch, or a router.

Will all this traffic be on one VLAN, or are you planning on having multiple VLAN's or subnets?
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Author Comment

by:kabrutus
ID: 36571514
All on 1 vlan.   I was thinking a bunch of  /22
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LVL 22

Expert Comment

by:eeRoot
ID: 36571588
If it's all one VLAN, then I would use one DHCP server.  If possible, I'd use the gateway router that these access points will communicate through.

A /22 subnet gives you 1024 addresses to use and a /21 gives you 2048.  Since you estimate seeing around 2000 addresses, I would round up to the next subnet range, and use a /20, for 4096 addresses.  That's a very large wireless network, but it's better to have too many IP's then too few.
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Author Comment

by:kabrutus
ID: 36571611
Can i do that with windows 2003 server?   If so,  can you help me break down how the ip's should start and finish?
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LVL 7

Expert Comment

by:Dusan_Bajic
ID: 36574328
If you will have 2000 clients connected to wifi at the same time you DO NOT want them in the same subnet, that's for sure. Any solid analysis of this problem requires much more info: what is your upstream speed, how much traffic do you expect that clients will request, will you guarantee any bandwidth per client or best effort only, are clients mobile within building (for example, person with wifi enabled phone moving between floors) or fixed (someone sits with laptop and doesn't move while surfing), how many APs will you have, do you have VLAN enabled switches... plus the RF planning side of the problem, which is completely separate issue.

Easy answer would be: setup DHCP on AP (different subnet on each) and let APs do the NAT.
Even easier answer (if you have zillion $$ in your pocket): call Cisco, they will do it for you.
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Author Comment

by:kabrutus
ID: 36574912
Thats another thing i was thinking about... having DHCP on the AP's.  My event is only for about a week, and all users will be roaming.  If i set different ip pools on the Ap's, will that make it harder for the wifi clients to roam?  I have enough Ap's.
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LVL 7

Expert Comment

by:Dusan_Bajic
ID: 36575015
What exactly is the AP brand/model?
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Author Comment

by:kabrutus
ID: 36575085
I have a few Xirrus X8
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LVL 7

Expert Comment

by:Dusan_Bajic
ID: 36575591
Looks like it supports roaming between devices, if you can figure out how to set it up. I can't give you any advice on that, never had one of those in my hands.
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Author Comment

by:kabrutus
ID: 36575622
They are really good systems.  I have used them in hotels before, but the hotel would supply the IP's.  Unfortuanly that is not the case this time around.  So i think i will just setup DHCP on the arrays instead of the a dhcp server.  All they need to do is browse the internet.  Can you check my ip configuration below an let me know if this will work?

start ip 172.16.22.2
end ip  172.16.23.254
SM       255.255.252.0
GW      172.16.22.1

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LVL 7

Accepted Solution

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Dusan_Bajic earned 2000 total points
ID: 36575979
If you go with 255.255.252.0 mask (which seems ok), it would be:

AP1:
start: 172.16.0.2
end: 172.16.3.254
sm: 255.255.252.0
gw: 172.16.0.1

AP2:
start: 172.16.4.2
end: 172.16.7.254
sm: 255.255.252.0
gw: 172.16.4.1

and so on....
Dont forget to enable NAT, and you should probably increase lease time to something like 3600 (seconds). Buiding will have to provide you IP parameters for gigabith eth interfaces.
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Author Comment

by:kabrutus
ID: 36576056
So lets say AP #10 does this look ok?

start ip 172.16.22.2
end ip  172.16.25.254
SM       255.255.252.0
GW      172.16.22.1

That seems like a lot of ips?  Can i just get away with?
start ip 172.16.22.2
end ip  172.16.23.254
SM       255.255.252.0
GW      172.16.22.1
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LVL 7

Expert Comment

by:Dusan_Bajic
ID: 36576160
If mask is 255.255.252.0, you can't start subnet with 22:
AP1: x.x.0.2 - x.x.3.254
AP2: x.x.4.2 - x.x.7.254
AP3: x.x.8.2 - x.x.11.254
...
AP10: x.x.36.2 - x.x.39.254

This gives you about 1000 addresses on 1 AP. Maximum number of users on one XN8 seems to be 512, but if you have many roaming users, one address will stay used even when user moves to another AP (until lease time expires).
You can use as many of these addresses as you like, just check that building is not using them. If they happen to use these exact blocks, you can use any other block form private range.
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Author Comment

by:kabrutus
ID: 36576216
This is what i am using...  I assume mine is wrong..  I am planing on about 14 pools. any chance on helping me fix these?  Thanks for your help so far.  as you can tell, im not a network guy...

Pool1      172.16.0.2 - 172.16.1.254 /255.255.252.0      172.16.0.1
Pool2      172.16.2.2 - 172.16.3.254 /255.255.252.0      172.16.2.1
Pool3      172.16.4.2 - 172.16.5.254 /255.255.252.0      172.16.4.1
Pool4      172.16.6.2 - 172.16.7.254 /255.255.252.0      172.16.6.1
Pool5      172.16.8.2 - 172.16.9.254 /255.255.252.0      172.16.8.1
Pool6      172.16.10.2 - 172.16.11.254 /255.255.252.0      172.16.10.1
Pool7      172.16.12.2 - 172.16.13.254 /255.255.252.0      172.16.12.1
Pool8      172.16.14.2 - 172.16.15.254 /255.255.252.0      172.16.14.1
Pool9      172.16.16.2 - 172.16.17.254 /255.255.252.0      172.16.16.1
Pool10      172.16.18.2 - 172.16.19.254 /255.255.252.0      172.16.18.1
Pool11      172.16.20.2 - 172.16.21.254 /255.255.252.0      172.16.20.1
Pool12      172.16.22.2 - 172.16.23.254 /255.255.252.0      172.16.22.1
Pool13      172.16.24.2 - 172.16.25.254 /255.255.252.0      172.16.24.1
Pool14      172.16.26.2 - 172.16.27.254 /255.255.252.0      172.16.26.1
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Author Comment

by:kabrutus
ID: 36576904
Ok, i think i got it... here is what i got...

Pool1      172.16.0.2 - 172.16.3.254 /255.255.252.0      172.16.0.1
Pool2      172.16.4.2 - 172.16.7.254 /255.255.252.0      172.16.4.1
Pool3      172.16.8.2 - 172.16.11.254 /255.255.252.0      172.16.8.1
Pool4      172.16.12.2 - 172.16.15.254 /255.255.252.0      172.16.12.1
Pool5      172.16.16.2 - 172.16.19.254 /255.255.252.0      172.16.16.1
Pool6      172.16.20.2 - 172.16.23.254 /255.255.252.0      172.16.20.1
Pool7      172.16.24.2 - 172.16.27.254 /255.255.252.0      172.16.24.1
Pool8      172.16.28.2 - 172.16.31.254 /255.255.252.0      172.16.28.1
Pool9      172.16.32.2 - 172.16.35.254 /255.255.252.0      172.16.32.1
Pool10      172.16.36.2 - 172.16.39.254 /255.255.252.0      172.16.36.1
Pool11      172.16.40.2 - 172.16.43.254 /255.255.252.0      172.16.40.1
Pool12      172.16.44.2 - 172.16.47.254 /255.255.252.0      172.16.44.1
Pool13      172.16.48.2 - 172.16.51.254 /255.255.252.0      172.16.48.1
Pool14      172.16.52.2 - 172.16.55.254 /255.255.252.0      172.16.52.1
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LVL 7

Expert Comment

by:Dusan_Bajic
ID: 36586149
that looks OK
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