topic Re: FlexConnect in a local network in Wireless

FlexConnect in a local network

B A — Mon, 05 Jul 2021 20:16:45 GMT

Hello,

I have basic knowledge of FlexConnect and when it's used - branch offices and remote sites. Recently I've been told by some auditors that we should configure FlexConnect in our local network to increase wireless speed and quality. I've never heard of using it in a local network. Does it make sense to enable FlexConnect in a local network?

Thank you for any feedback.

Btw. we have one WLC and 70 APs.

Re: FlexConnect in a local network

Mark Elsen — Fri, 07 May 2021 11:17:37 GMT

> ...to increase wireless speed and quality.

I doubt this, flexconnect only offers user connectivity through local switching when the controller is unavailable , this normally does not happen.

Re: FlexConnect in a local network

B A — Fri, 07 May 2021 12:04:49 GMT

Do you see any benefits in configuring FlexConnect in a local network?

Re: FlexConnect in a local network

balaji.bandi — Fri, 07 May 2021 12:14:06 GMT

Personally i do not see any advantage as you mentioned with orginal post.

Re: FlexConnect in a local network

B A — Fri, 07 May 2021 12:22:05 GMT

Ok. And any other possible advantages?

Were auditors wrong?

What is your opinion on this in general?

Re: FlexConnect in a local network

Mark Elsen — Fri, 07 May 2021 14:29:28 GMT

>Were auditors wrong?

- Because your locally-switched-intranet , these days , is at least 10xfaster then average wireless speeds -> no advantage.

Re: FlexConnect in a local network

saravlak — Fri, 07 May 2021 15:53:02 GMT

For local campuses scenario i've never deployed flex-connect mode, if there's no special use cases and everything already works fine then don't make any changes. only places have deployed flex in-campus is when there's cloud WLC in place.

Wireless speed and Quality don't change between flex and local mode -it's the same LAN/WAN link at the campus, it's only the uplink datapath that makes the difference.

From a wireless traffic perspective, it's capwap(local-mode) Vs no-capwap(flex-mode) to upstream and it doesn't make big difference in LAN.

Also, there'll be overhead to maintain WLAN-VLAN flex config and relevant switch trunk config needed in the current environment and whenever the network grows.

hope it helps to understand from high-level.

Re: FlexConnect in a local network

Rich R — Sat, 08 May 2021 14:35:07 GMT

In general - no reason why flex should make any difference for your scenario but there is 1 reason we configure all our APs as flex - whether we're using them for flex or not. We use "MAC Filtering" with central auth by radius server on some WLANs. As the radius is sometimes proxied to 3rd party radius servers on the other side of the world the client association attempt often fails due to up to 1200 milliseconds for radius response when they're in local mode. There is no config to mitigate this in AireOS according to TAC. But changing the AP to flex mode magically resolves the problem (without changing any other config) so that we no longer have the timeouts and client association failures - problem solved. This was the TAC recommended solution and has worked perfectly for us ever since.

I doubt that this is an issue for you but a useful bit of info for anybody who might have a similar problem in future.

Re: FlexConnect in a local network

saravlak — Sat, 08 May 2021 15:20:39 GMT

this appear to be a bug in code or incorrect config that should be fully isolated, you should ESC the issue within Cisco Engg to properly get it resolved.

Re: FlexConnect in a local network

Rich R — Sat, 08 May 2021 16:06:10 GMT

Like I said the workaround (flex mode) solved it for us with no downside so why would we go to the trouble of raising a feature enhancement bug (if you've ever done that before you'll know why it's best avoided) knowing that it could take months to years to get a release with the enhancement (and only if Cisco decide to implement it). Adding new knobs to tune something is invariably treated as an enhancement not a bug. As far as Cisco were concerned it was working as designed and there was a perfectly palatable workaround. I was just highlighting it for awareness in the context of the question being asked (reason for using flex mode). We are very familar with opening bugs (we've opened dozens and got them fixed) as well as enhancement requests and there is no point in wasting further time and energy on something like this which was not a show-stopper with the workaround. That energy is best expended on the real show-stoppers which do require a fix or enhancement from Cisco. As the saying goes - choose your battles wisely...

Re: FlexConnect in a local network

saravlak — Sat, 08 May 2021 16:08:07 GMT

in your setup/design, Challenge/Ask your auditors to prove through demo or Cisco doc that shows Flex better over local -Both deployments works though.

FlexConnect Feature Matrix
https://www.cisco.com/c/en/us/support/docs/wireless/5500-series-wireless-controllers/112042-technote-wlc-00.html

Re: FlexConnect in a local network

B A — Mon, 10 May 2021 08:19:46 GMT

Thank you all for your comments. I appreciate it.

I know both deployments work. I am just trying to understand if configuring FlexConect would be beneficial for us as auditors told us.

@saravlak "it's only the uplink datapath that makes the difference.", "it doesn't make big difference in LAN"

The traffic from/to WLC would reduce but is this change worth it? Would the traffic reduce significantly so it would actually affect the network performance? Is this a reason why we should switch to FlexConnect?

We have 70 APs and each of them usually handles 5-25 clients and a total number of clients don't exceed 450 clients at one time.

Re: FlexConnect in a local network

saravlak — Mon, 10 May 2021 10:30:49 GMT

Local mode is widely deployed model on campus LAN and Cisco doesn't push flex over local mode on Campus LAN for wireless speed/quality reasons, unless its cloud WLC in use period.

in your network, If WLC is not a bottleneck then there is no reason to worry about wireless speed/quality. also, if there's no complaint from end-user from user experience perspective then don't make any change on existing setup.

Re: FlexConnect in a local network

saravlak — Mon, 10 May 2021 10:53:14 GMT

I agree with you, however, That was a direction/guidelines, its not necessary it should be followed and can be ignored based on the given situation and other requirements. Coming from Cisco, not all Cust will easily take changing the design as soln. for a given critical issue/basic feature. To give an example, let say big retail stores got 1000s of stores and they hit this issue, we don't expect them to change the design for this given issue which is unacceptable. As you said in your case its not needed but that's not the case everywhere and it goes case by case basis.

Re: FlexConnect in a local network

B A — Mon, 10 May 2021 13:02:09 GMT

Well, users complain occasionally but I don't think it's important in this story.

Anyway, what negative impact could it have if we enable FlexConnect?

Re: FlexConnect in a local network

saravlak — Mon, 10 May 2021 16:53:18 GMT

As captured before, there's no negative impact but there's overhead to redesign/reconfigure the network appropriately to accommodate to flex and continue do so when new APs were added. Also, now the physical WLC can be replaced with cloud wlc, if and when needed.

Re: FlexConnect in a local network

Scott Fella — Mon, 10 May 2021 17:00:14 GMT

Here is my 2cents. Back in the day's when the 2504 came out, folks were worried about the backplane being an issue so some converted to flexconnect. I have seem large environments where the customer had 5508's as an example and only had one port connected to the network. So the myth is, does it really help, I don't really think so unless you are crossing the WAN and you want to have majority of the traffic to stay local. You need to also keep in mind the limitations of flexconnect and make sure that, if you decide to go this route, that the limitations doesn't hurt your design and your existing user experience. Layer 3 roaming is not supported and there is also a limitation on the number of ap's in a flexconnect group. Review the flexconnect guide and make sure you understand the various scenarios and limitations specified in that guide.

You can also test with one ap and actually see if the auditors theory is valid in your situation. Sometimes filks keep what they hear and see in other environments as "the correct way". That is not always the case.

Re: FlexConnect in a local network

Rich R — Mon, 10 May 2021 21:34:43 GMT

I'll add my 2 cents worth too ...

While saying flexconnect like Scott says you do need to check the feature matrix because some features you may be using may not be supported in flexconnect mode. But actually I suspect your 'auditor' (quotes intentional because probably just someone with no technical knowledge of WLC just following a tick-list template) is actually saying you should implement flexconnect LOCAL SWITCHING because just changing to flex won't make any difference at all (apart from the aforementioned feature support) - do they realise that?

So assuming you changed to flexconnect local switching there is a theoretical gain to be made:

- traffic is no longer being tunnelled in CAPWAP so you could see 1 or 2 ms reduction in latency (removing encapsulation/decapsulation of the traffic).

- the WLC is no longer a bottleneck for the traffic (like Scott said) but if you're within capacity unlikely to make any difference.

- because the traffic is no longer being tunnelled in CAPWAP you can use a larger TCP MSS (1250 is recommended with local mode or flexconnect central switching, has no effect on flex local switching) which could offer some improvement in throughput and less fragmentation of UDP traffic.

You could test to see how much difference these actually make in practice, and then do a cost (of redesign) vs benefit analysis to make an informed decision. In all likelihood I expect the improvement will be marginal (of the order of 10% my best guess) and likely not justify a redesign. Chances are users would not notice any difference anyway apart from speedtest improving slightly.

Re: FlexConnect in a local network

Scott Fella — Tue, 11 May 2021 03:53:47 GMT

You typically don't, at least I have never seen any slowness. Now with the vWLC, you might want to consider FlexConnect and not local as traffic would tunnel back to your VM host. Best thing you can do is test for yourself. Like I said, you can take a spare AP and configure that for FlexConnect, you will need to create a new SSID so you don't mess with production SSID, unless you are comfortable making changes to the existing to enable local switching.

If you take what many experienced engineers here have provided in your post, none have stated that FlexConnect provides better throughput. Let that sink in for a while and make a decision on what your next steps would be.

Re: FlexConnect in a local network

B A — Tue, 11 May 2021 11:59:36 GMT

Thank you for your feedback.

@saravlak No negative impact. Got it.

@Scott Fella "You can also test with one ap and actually see if the auditors theory is valid in your situation"

How would you test it? What should I measure and on which devices?

@Rich R "You could test to see how much difference these actually make in practice"

How should I test it?

Are you all saying that configuring FlexConnect makes sense only when WLC uplinks aren't enough for the traffic?

We have one WLC with 2x1GB uplinks that handle 70 APs with 300 to 450 clients. Do you think this is not enough and we should change something?