local vs flexconnect which is better for throughput

[JASON SIMMONS]

We have 190 APs in two buildings on the same campus connected to 2 5508 controllers.  Would it be better to put these APs in flexconnect mode with local switching?  My thought is that traffic would be better to have traffic switched at either the access switches on each floor or the main switches for each building rather than traveling back to the core, through the controllers and then to its destination.

[Sandeep Choudhary]

Hi,

You must use local mode because all AP are at same place menas in one campus.

Flexconnect is good when you have a remote office and there some APs are connected.

So i will recommand to use in Local mode.

Regards

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[Ashish Chandra]

Use flexconnect for remote site where you dont have any controller available and you still want to manage it remotely.

Local switching will suit your situation as everything is in the same campus.

[kaaftab]

In local mode,is also know as centrally switched and trafiic is switched(bridged) from the ap to the controller where it is then routed by some routing device.

Flex Connect also known as HREAP  allows data traffic to be switched locally and not go back to the controller like an autonomous AP, but managed by the WLC.  In this mode, the AP can still function even if it looses connection with the controller anytime you want to switch traffic locally, that would be the time to use Flex Connect. 

So its depends on the deployment design as for remote deplyment flex connect takes the lead.

[Florin Barhala]

Hello Simmon,

As I see it I find your question very interesting. You just want to know which of the two deployment scenarios could lead into more performance.

Never test it in parallel the two sollutions but I believe you got to give it a go and test yourself. You can deploy all APs in local mode and leave 5 for FlexConnect mode.

From outside FlexConnect local switching seems to have the lead, but I can't wait to see your results.

[franklinb]

SIMMONSJASOND - have you implemented this already? I would love to know what your findings were.

I am looking at campus design and can't understand 100% why it is suggested I use central switching instead of FlexConnect. Yes I have a DC here (for now) and when I won't it will still have 2 x 10Gbps link to the nearest DC but the Controller (5508) only has 8 x 1Gbps links... surely it's better performance for a 500-person campus to use FlexConnect to reduce load on the controllers.

Does FlexConnect local switching mean that I lose some roaming features?

[Rasika Nayanajith]

FlexConnect is not scaled for a campus & it is designed for branch deployment. You will find certain limitations in this FlexConnect design & roaming is one of them.

HTH

Rasika

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[franklinb]

I understand that's what the documentation says (and keep hearing repeated without any clarification) but surely it all depends on your situation.

Take this example for instance:

- A 500-seat campus broken into 4 buildings

- AP's managed by a HA-pair of 5508's in two DC's (10Gbps ring < 5ms), one DC on the main campus, connected by 6 x 1Gpbs EtherChannel

- Less than 25 AP's per building

Surely the only issue then if we used FlexConnect local switching for a WLAN for Corporate PC's would be roaming. That isn't really much of a problem for PC's - who really wanders around a campus with their laptop open wanting persistent connection between sitting down?

If you have multiple 802.11ac clients connecting to 3702 AP's that 6Gbps bottleneck is going to be saturated fairly quickly.

As far as I can see FlexConnect groups are limited to 25 AP's but again that's not a huge issue given the usage case.

For mobile devices (tablets, phones) and guest access then you can still use central switching.

[Rasika Nayanajith]

I agreed, all depends on your situations

For that sort of numbers, I would still think central switching local mode AP give simpler solution to manage. Your consumer traffic demand won't go up just because using of 802.11ac clients.

Think about wired user perspective, if you have 48x1G port what is the realistic uplink usage ? Most of time 1Gbps is sufficient for a client traffic demand. Same goes to wireless, where you have 10x3702 in the switch, it does not mean you require 10G uplink from that switch. So I would surprise if you can get traffic to saturate 6 or 8 Gbps of your WLC using the numbers you have given.

I am not saying FlexConnect won't work, but you have to choose what is the best for the requirement you have.

Unified wireless-CUWN, Unified Access - CA, FlexConnect, Autonomous are different design models targeted for certain use cases.

HTH

Rasika

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[amalitol81]

---

Hi, Now I'm having this same discussion. Previously I had some considerations about using FlexConnect on 25 APs that will be deployed on our campus.  The interesting part is that we want to implement our wireless network connected to a Cisco ISE platform, that is actually  working for AAA for our wired users. 

My plan is to connect the WLCs (SSO-HA) on the aggregate user switches and use the same VLANs users are using right now.

In our current configuration users use a certificate for authentication and ISE assign a specif VLAN based on the certificate template. We want to use the same configuration for wireless, but we don't know which option (FlexConnect vs Centralized) is better.

My thought is that FlexConnect mode will have some limitations and I do not see any advantage on this implementation. 

Please correct me if I'm wrong:

Limitation deploying FlexConnect on a campus:

- We have to use the management (capwap) vlan as the native vlan.

- More difficult to manage.

- QoS applied to traffic passing through WLCs won't be applied. 

- Roaming capabilities are reduced.

- I DON'T KNOW IF THERE ARE SOME OTHERS LIMITATIONS WHEN YOU USE CISCO ISE.

Advantages of deploying flexconnect on the campus 

- Maybe prevent the bottleneck that could occurs on the LAG interfaces on the WLCs.

- ARE THERE ANY OTHER ?

Thank you guys,

[amalitol81]

Hi, Now I'm having this same discussion. Previously I had some considerations about using FlexConnect on 25 APs that will be deployed on our campus.  The interesting part is that we want to implement our wireless network connected to a Cisco ISE platform, that is actually  working for AAA for our wired users. 

My plan is to connect the WLCs (SSO-HA) on the aggregate user switches and use the same VLANs users are using right now.

In our current configuration users use a certificate for authentication and ISE assign a specif VLAN based on the certificate template. We want to use the same configuration for wireless, but we don't know which option (FlexConnect vs Centralized) is better.

My thought is that FlexConnect mode will have some limitations and I do not see any advantage on this implementation. 

Please correct me if I'm wrong:

Limitation deploying FlexConnect on a campus:

- We have to use the management (capwap) vlan as the native vlan.

- More difficult to manage.

- QoS applied to traffic passing through WLCs won't be applied. 

- Roaming capabilities are reduced.

- I DON'T KNOW IF THERE ARE SOME OTHERS LIMITATIONS WHEN YOU USE CISCO ISE.

Advantages of deploying flexconnect on the campus 

- Maybe prevent the bottleneck that could occurs on the LAG interfaces on the WLCs.

- ARE THERE ANY OTHER ?

Thank you guys,

[patoberli]

If you have all APs on the same Layer 2 network, go for local mode. There are also other limitations in Flexconnect, depending on your AP model (check the release notes of the software you want to use on the WLC for details).
It's extremely rare to high a bottleneck on the LAG interfaces on the WLC, not to forget that you can combine 8 times 1 Gbps on the 5508. Here, with ~180 APs (nearly all 802.11ac now), with ~1800 wireless clients, I very rarely hit > 1 Gbps on the 10 Gbps interface of my 5520. And I have 80 MHz channels activated, students and an open internet connection ;)

[NotJane]

Hi, 

May I please ask you about the specifics of the roaming limitation in Flexconnect design?

[Scott Fella]

@NotJane The FlexConnect guide depending one what controller model your are using will first state the max number of access points you can have in a FlexConnect Group.  Roaming within a FlexConnect Group is supported and works well, but if you have more AP's and have to have two FlexConnect Groups, then the roaming between the two is not supported.  You can get away still using FlexConnect, if you separate the groups where folks might not roam, which might be between building, tunnels, floors, areas where users would not be using their devices while walking, etc.  

Take a look at the FlexConnect guide depending on your controller you have.  Here is one for the 9800's.
FlexConnect (cisco.com)

[JPavonM]

HEre you have some other limitations (or features) for flexconnect deployments:

FlexConnect Feature Matrix