Adding a second controller - 3750G integrated WLC

Answered Question
Sep 24th, 2009

Hello all -

I'm new at this, so please bear with me.

I've been tasked to add a second WLC to a customer's network. They currently have a 4402-50 supporting 47 access points. The customer purchased a 3750G w/ integrated WLC (50AP) anticipating the addition of several more APs, but the addition is on hold. In the meantime, the customer would like the new WLC to help balance the AP load. The existing WLC is running 6.0.182.0. The customer has a mix of 1130, 1240, 1140 and 1250 APs. They are starting to use N features.

Both controllers are now on the same subnet 10.1.113.x. I've upgraded the code on the 3750G_WLC to match the other controller. Here are some questions I have now:

1. Am I right to think I need to set these two controllers in the same mobility group?

2. Am I right in thinking I will need to manually configure each AP to point to the controller I want it to be associated with? In other words, is there an AUTOMATIC load balancing feature? (NOTE: The customer just purchased and will have installed WCS)

3. Once we exceed 50 APs, will any other configuration changes need to happen?

This is all a little sketchy for me because we are right at the limit. So.. right now we are N+1 asking to load balance between the two. Once we exceed 50 APs, we're no longer N+1 and will need to designate which APs are high priority in case of failover.

Any tips on installing this second WLC into the network and any recommendations you may have for managing these 47 existing APs is appreciated.

Cheers -

I have this problem too.
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Correct Answer by weterry about 7 years 2 months ago

So, when you define primary and secondary Controller, you specify the name of the controller. In 5.2 and above you also can specifiy the Management IP address of that controller. The AP will learn about these controller through the mobility group defined on the controllers.

About losing the controller, I didn't mean to configure priority after the fact. I meant that if you are trying to define priority (for the event that a controller was lost), then you would set the priority on the High Avail tab on the AP configuration. You would want to this when you install everything to begin with.

If you do not define primary/secondary, the AP should learn about the controllers from each controller, and when the controller sends its discovery replies, it should specify which one to load-balance to. Or something like that.

The bottom line is that if you don't have a primary/secondary defined, then the AP discovery process should get your AP on the least occupied controller. It is primary/secondary definitions that kind of overwrite this, which is what I was calling a "manual" load-balancing...

Does that help any more?

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weterry Thu, 09/24/2009 - 17:45

Sounds like you are on the right track.

1) yes, put the two in the same mobility group (and make sure you make the two controllers aware of each Controllers > Mobility, you should have the MAC and IP of each controller in both controller's mobility list)

2) If you want to define primary and secondary controllers, then this would not be an "automated" load-balancing. But it is an option. This way you know which AP is on which controller.

Alternately, if you do not define Primary/Secondary, then the APs SHOULD load-balance when they discover and join the controller.

3) I don't follow. Each Controller can support up to 50 Aps. As long as you don't go over 50 Aps each controller, nothing should need to be done.

NOW, if you lose a controller, then YES, you want to configure the Priority of your APs on the High Availability TAB.

I recommend you set 1 AP to LOW priority for each 1 AP that you set as HIGH/Critical.

Ideally, if you lose a controller (or path to it), then the Lower priority APs will drop off a controller and make room for the higher priority APs.

Did this help any?

bdunsing2 Thu, 09/24/2009 - 20:58

Thanks - Yes - for the most part.

On 3) I meant if we define primary and sceondary for load balancing, and one controller fails, how will the APs know where to go? I believe the APs with a defined primary address of the controller that fails would be lost.

Your statement about losing the controller confuses me a bit. You say "if you lose a controller, then YES, you want to configure the priority.....etc". Is this something ou would do AFTER you've lost the controller? How would you then reach the "orphaned" APs? BY setting the remaining one to MASTER, capturing the AP, then configuring the High Availability?

And finally - if I do not configure Primary/Secondary, and 47 APs are already joined to the original controller, how do I get them to load balance automatically with the new controller?

Thanks for you help!

Correct Answer
weterry Fri, 09/25/2009 - 09:35

So, when you define primary and secondary Controller, you specify the name of the controller. In 5.2 and above you also can specifiy the Management IP address of that controller. The AP will learn about these controller through the mobility group defined on the controllers.

About losing the controller, I didn't mean to configure priority after the fact. I meant that if you are trying to define priority (for the event that a controller was lost), then you would set the priority on the High Avail tab on the AP configuration. You would want to this when you install everything to begin with.

If you do not define primary/secondary, the AP should learn about the controllers from each controller, and when the controller sends its discovery replies, it should specify which one to load-balance to. Or something like that.

The bottom line is that if you don't have a primary/secondary defined, then the AP discovery process should get your AP on the least occupied controller. It is primary/secondary definitions that kind of overwrite this, which is what I was calling a "manual" load-balancing...

Does that help any more?

bdunsing2 Mon, 09/28/2009 - 20:59

I believe so. Your last sentence really made sense to me. Thanks for going the extra step to further explain!

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