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Wireless Controller 5508 Network Design Question

Unanswered Question
Apr 19th, 2012
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I recently took over the wireless for my organization because the previous administrator left. We are a HealthCare organization with multiple onsite Campus Buildings within 1/4 of a mile of each other connected via fiber.  We have recently added a large number of access points to both our main hospital as well as some of the other Campus buildings because of a recent roll out of a particular hospital application that all of the physicians need. My concern is that the way that the Wireless network was initially designed that in it's current topology we will experience latency problems. Which I was told last week we started having. We have 2 Cisco 5508 Wireless Controllers (wifictrl1) and (wifictrl2).  Each attached to a Cisco 6509E Series Core Router respectively ( Wifictrl1------->  Core  A)   (Wifictrl2 ------>  Core B) via 4 Gig LAG trunks.  Both of the wireless controllers are configured in the same mobility group.


Controller firmware version :     7.0.220.0


Network Setup :


Both the wireless controllers management interfaces are configured on vlan 240.  (172.20.240.x   255.255.240.0 )


wifictrl1   172.20.240.15

wifictrl2   172.20.240.16

Virtual Interfaces on both controllers are   1.1.1.1

Service Port   192.168.1.1


We have one SSID (mmg_wireless) that is setup for clients to connect to throughout the entire organization. Everyone connects to this SSID for all hospital application resources.  When clients connect to this SSID a dhcp server gives them an ip address on the vlan 240  (172.20.242.0 - 172.20.248.255)


My questions are as follows:


Is it Cisco best practices to create one large Vlan that contains both controllers, ap's and clients all in the same network ? Or should I be segmenting the network a particular way?


With my current Wireless Controllers is it possible to segment the wireless network by building into seperate networks (vlans)

but still allow clients to connect to the (mmg_wireless) ssid and roam throughout the campus without mobility and roaming issues?


Is it necessary to segment my wireless network by creating more vlans instead of putting all of the ap's controllers and clients all in the same network? Will having all of my wireless devices in the same subnet degrade my wireless network because everything is in the same broadcast domain?


Is there a maximum recommended number of ap's that should be on a controller at any given moment? I currently have 200 ap's on one controller.

with 672 clients currently conencted to them. (360 of them are connected to the mmg_wireless ssid) .


Is it best practice to seperate the maangement ip's of the controllers and ap's from the client vlans?


That is all for now. I am new to wireless , but I am learning more and more everyday.  Any help is appreciated.

Please let me know if I need to provide additional information .  I would be glad too.




Thank You,


Tony

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George Stefanick Thu, 04/19/2012 - 12:33
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May I ask, what is your latency ?

warknite49 Thu, 04/19/2012 - 12:51
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The latency for the connection averages around 13 ms.

every 30 -40 pings the latency jumps to 150-180 ms.

we have an application that is getting disconnected frequently from the wireless.


thank you,


Tony


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George Stefanick Thu, 04/19/2012 - 12:55
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Tony,


What application are you using? I am also in a large healthcare enviroment, 6000+ wifi devices.


In most cases, 13 ms isnt bad. And in fact anything under 150ms is voice grade. If your apps are discnnecting becuase of 150-180ms, its something else, IMHO.


BTW -- Steve is spot on in his reponse. We here have /21 subnets with little issues. I closley monitor the links.

Stephen Rodriguez Thu, 04/19/2012 - 12:41
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Is it Cisco best practices to create one large Vlan that contains both controllers, ap's and clients all in the same network ? Or should I be segmenting the network a particular way?


     Not best practice.  Segmentation is up to how you want to do it for the most part


With my current Wireless Controllers is it possible to segment the wireless network by building into seperate networks (vlans) but still allow clients to connect to the (mmg_wireless) ssid and roam throughout the campus without mobility and roaming issues?


     yes, you could use AP groups and do a subnet per building.  the traffic will still backhaul to the WLC then to the core.  So if the latency is the fiber between the buildings you would still have an issue.  you could also use FlexConnect, but would need to know more on how the application is supposed to work to answer that better


Is it necessary to segment my wireless network by creating more vlans instead of putting all of the ap's controllers and clients all in the same network? Will having all of my wireless devices in the same subnet degrade my wireless network because everything is in the same broadcast domain?


     IMHO, I think the AP should be in their own VLAN, and the WLC can live in the 'server' vlan if you want.


Is there a maximum recommended number of ap's that should be on a controller at any given moment? I currently have 200 ap's on one controller.

with 672 clients currently conencted to them. (360 of them are connected to the mmg_wireless ssid) .


     how many ports are you using to connect to teh 6509?  if you are using all 8 ports you should be fine.


Is it best practice to seperate the maangement ip's of the controllers and ap's from the client vlans?


          answered above

warknite49 Thu, 04/19/2012 - 12:57
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My concern is that by configuring different parts of the hospital on different vlans. that roaming from one access point to another on the mmg_wireless ssid will become a problem. If a client on vlan 50 moves to an ap a different vlan will it disconnect the client?


Thank You,


Tony


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Stephen Rodriguez Thu, 04/19/2012 - 13:01
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No, when you roam between AP groups on a WLC, or between WLC that have different subnets for the same WLAN, you will do a Layer 3 roam.  Your device will keep its current IP address and continue to pass traffic like nothing has happend.


In a AP group roam, it's still on the same WLC, so the WLC just updates the MSCB with what AP the client is connected to.


in the case of a inter-controller roam, it's a bit different.  When the client roams from WLC-A to WLC-B, WLC A will become the 'anchor' for that client.  All traffic will ingress/egress from this WLC.  traffic flow would be:


Client ---> WLC-B <---mobility tunnel<--->WLC-A<---> network, and the reverse for traffic destined to the client



Steve

George Stefanick Thu, 04/19/2012 - 13:04
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No, so long as you have mobility set up correctly. The client will ANCHOR itself to the first WLC it connects to. If the client moves to another ap from a difference WLC / SUBNET it will send its traffic through the tunnel to the orginal controller. In fact if you look at your CLIENTS tab you will see 802.11(mobile). This is a client who is connect to a WLC and sending their anchor traffic to a difference WLC.


This works, it sounds messy or slow. But its really not, IMHO.

George Stefanick Thu, 04/19/2012 - 13:06
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Its S + S !


Man you boys were up late last night ... You couldnt sleep or what ?

Stephen Rodriguez Thu, 04/19/2012 - 13:23
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Heh, sleep was not my friend last night. And the alarm went off too early this morning


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warknite49 Thu, 04/19/2012 - 12:59
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I am currently using 3 of the 8 ports on the controller with 200 access points.


Thanks,


Tony


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Scott Fella Thu, 04/19/2012 - 13:02
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Might as well put my 2¢


If a client roams, that device will keep its ip address unless it disconnects from the wireless and the device has to re-ip.  as far as 200 AP's on 3 ports, that is fine... I have a client that has only one port with 200+ because they havent yet decided if they want to add another port.

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